How do you choose the right VoIP Service Provider?

VoIP Service Providers – the core services on offer

Business and home users all have to choose from roughly the same pool of companies providing VoIP services, but the things that they are looking for may not completely overlap. Let’s consider a few of the more important services provided.

Cheap calls

Why use VoIP? Answer – cheap or free calls. For the home user, this generally means calls to friends and family, especially where some of them are living abroad. For a business, a 25% saving on the cost of outbound calls could equate to a lot of money – and telephone costs go straight to the proverbial “bottom line” so there is a strong incentive to keep them down. Using VoIP it is even possible to make and receive calls at any time of day with a cost per minute of zero. For more information about making free SIP-to-SIP calls, click on this link.

Cost per minute of a call from the UK to the United States using various carriers:
Based on published data on 13th Feb 2009

Standard BT off-peak BT International Saver Sipgate VoIP Voiptalk Silver
11.26 p/min 2.94 p/min 1.5 p/min 0.9 p/min

Cost per minute of a call from the UK to an Australian mobile phone using various carriers:
Based on published data on 13th Feb 2009

Standard BT off-peak BT International Saver Sipgate VoIP Voipfone VoIP
35.72 p/min 29.36 p/min 15.1 p/min 12.2 p/min

Inbound numbers

When you sign up for a VoIP account with one of the VSP’s, you will be assigned an inbound number. The cheapest packages that you can sign up to will mostly provide a “non-geographic” number such as one beginning 056 or 0844. Calls to these non-geographic numbers are usually a little bit more expensive than calls to ordinary landlines (geographic) and the extra revenue is shared between the carrier and the service provider. So your VSP is collecting a small payment for every inbound call made to your VoIP phone.

If it is important that your number can be called from outside the UK, make sure you check with your provider because some non-geographic numbers cannot be called from abroad.

Geographic and International numbers
Once you get away from the cheapest packages, your choices for inbound numbers generally improve. You should be able to get a geographic number for the location where you live (or for some other UK location if you prefer). Some VSP’s can also offer International numbers that may be added to your service. This could be very useful for a business that wants to encourage calls from other countries or even wants to make it appear that they have a local office in that country.

Free-phone numbers
Perhaps you are running a business and want to provide a free phone number for your customers to call you on – just ask your VoIP provider. They will almost certainly be able to offer you such a number at a reasonable charge, but take note that, in addition to the setup charge and possibly a monthly recurring charge, there is usually a small per-minute fee on every inbound call made to you on that number. The calls are free to your customers, but not to you.

Some providers can also offer free-phone numbers in other countries, such as the U.S.

Premium rate numbers and personal numbers
Premium rate numbers are another example of non-geographic numbers and some of them suffer the same restrictions regarding accessibility from outside the UK. Premium rate numbers are almost the opposite to free-phone numbers – the caller pays more and therefore you should be paying less. With some premium rate numbers you can even receive revenue for every call. However, you should check carefully what the charges are for these inbound numbers and what you may receive – in many cases the VoIP provider allows you an offset against their usual charges or makes no charge for the inbound calls (in cases where non-premium rate calls would have incurred a charge). For some inbound premium rate numbers you may receive revenue for each call. Numbers starting with 0870 and 0871 are probably the most common premium rate numbers in the UK – the latter costs more per minute than the former and it is even arguable whether 0870 is actually a premium rate number at all. The serious premium rate numbers are the ones starting 090, 091 or 098 which are 11 digits long. Also watch out for the so-called personal numbers that start 070 – these look rather like a mobile number, but they can cost the caller up to 50p a minute.

For more details about premium rate numbers check the PhonePayPlus web site.

DDI numbers
DDI stands for Direct Dialing Inward and it traditionally refers to numbers allocated in a block to businesses – the business is then able to deliver calls direct to the phone on a person’s desk without the need to go through the operator or receptionist. VoIP service providers often refer to inbound numbers as DDI’s, especially in conjunction with a SIP Trunk. It usually just means that several different numbers (usually consecutive) are assigned to one account and the dialled number is sent to the customer premises equipment where it can be used to route the call. The term is often used rather loosely in the VoIP world and sometimes just refers to a single inbound number.

SIP Trunks

SIP Trunks are designed primarily for businesses – they would normally connect to an IP PBX at the business premises. Asterisk would be suitable as a business PBX in this role. SIP Trunks have the ability to carry multiple simultaneous calls. Very often, they will also support multiple DDI numbers for inbound calling. This means that your business can publish several different numbers, each of which is routed independently by the PBX to a different department or a different employee.

Additional Services

The list of add-on services is very long so we will not even attempt to provide details here. It will include things like voicemail, call forwarding, missed call alerts, virtual PBX, IVR menus, call recording, conferencing, etc.

Factors to consider when choosing a VoIP package

A word of caution before you buy

Remember that your VoIP phone or IP-PBX solution will require reasonably good high-speed Internet access. For a home user making one VoIP call at a time, this usually just means a reasonable broadband connection. For a business or where several simultaneous calls are required, it may be necessary to upgrade or even install a new broadband connection dedicated exclusively to voice. Sharing your Internet connection for voice and data at the same time can lead to intermittent problems of garbled or broken speech – this applies for home users too. I have to check that my son is not downloading some large file whenever I want to use my VoIP phone at home, even though we have cable Internet. If you are using ADSL, then the problems are likely to be even greater – it is assymetric (slower uploading than downloading), speed depends a lot on your distance to the local exchange and the quality of the copper cables in the “local loop”. Also, it usually is a shared resource so it suffers from “contention” – i.e. the more people in your street are using their broadband, the slower it is for all of you.

Prices and packages

Call charges are important and will probably be the main deciding factor for many users. Think carefully about the type of calls you make. The price variations between different providers are not consistent across all call types – some providers are cheaper for International calls but not for national call. Some charge more for calls to particular mobile carriers while other do not – for example, Sipgate charge 9.9 p/min for all UK mobiles yet Voiptalk Silver costs 9.5 p/min to most mobiles but a hefty 18.5 p/min to “Mobile Three”. Some even charge for calling 0800 free phone numbers. So try to match your pattern of useage to your provider.

Look at the packages available and see if it makes sense to pay a monthly fee for cheaper call costs or for bundled minutes. Some providers offer so-called “Unlimited” calling to UK landlines and certain International numbers. These are subject to fair usage policies (hardly surprising) but they may still be the right solution for users who make a lot of calls. Read the small print carefully though, or you might be paying extra for bundled minutes only to find that the numbers you call most often are not included.

Please click here to view our VSP comparison table

Some less obvious factors

Simultaneous calls:
Some providers limit the number of simultaneous calls. You will be limited anyway by the bandwidth and speed of your broadband connection, but accounts designed for low volume users will sometimes have a cap of 2 simultaneous calls. This is done basically to prevent abuse and to make sure you are not trying to be too damned clever – for example using a home user account for a small business. It also allows providers to make a distinction between single user SIP accounts and so-called “SIP Trunks” for which they charge extra (see SIP Trunks above). However, even if you only have one IP phone, it can be useful to be able to make two simultaneous calls. The most likely scenario for a home user to need more than one call channel, is to allow you to put one call on hold and then make a new call to another user – most multi-line IP phones will then allow you to shuttle between the two calls or even to conference the calls together.

Multiple phones using the same registration
This will not be important for most users, but for a few it could be an important factor. Suppose you want two different IP phones to ring at the same time when an inbound call arrives – perhaps one phone is in your office and the other is at home. If your provider supports multiple phone registrations on the same account then it will be possible. Usually, when multiple registrations are allowed, all the phones will ring simultaneously. The first one to answer gets the call – the others should stop ringing as soon as the first answers.

Outbound calls charged per minute or per second
This may sound trivial, but if you make a lot of short calls, then you could end up paying quite a lot more if your provider charges for a full minute whenever a fraction of a minute was used. For example, a call lasting 2 minutes and 6 seconds would be charged as if it were a 3 minute call by some providers. Others would only charge you 2.1 times the cost per minute. If most of your calls last a long time then this will have less impact and you should probably look more at other factors when choosing a provider.

Prices quoted with or without VAT
If small price differences are important to you then make sure you are comparing like with like. Some providers make it very clear on their web sites if the prices include VAT or not. Others are much more vague or make it downright impossible to tell. If they don’t mention VAT then assume it is not included. This applies to the initial and monthly package costs especially. The prices quoted for per-minute call charges almost always exclude VAT. The only exception I know of is Sipgate who include VAT in the call prices they quote to UK customers, albeit at a rate of 19% because they are a German based company.

Open networking and interconnection with other providers
This subject is discussed in some detail on another page:
Link to page about free VoIP calls.
VSP’s make little mention about this on their web sites, especially those that restrict calls to other providers. The only UK provider we have identified so far that offers completely open access to other SIP providers is Freespeech. They also have good prices (VAT indicated clearly) and a nice easy-to-understand web site. They don’t limit the maximum number of simultaneous calls either. The only gripe I have with them is they charge for 0800 free phone calls.

Freespeech win the prize as far as I’m concerned, but this is on the basis of quite limited research and I would be happy to hear feedback from others. Send me an email at info(at) By the way, in the U.S., try Callcentric because they are one of the few providers who will allow direct calling to other SIP providers. You may find this review useful too