I get asked this so often, that I've written a full answer for it. If you need to know more give us a call on 020 7043 5555.
How to get a new number and divert it to your mobile (or any other number)
I answer this question more than any other here so forgive the pre-prepared answer; its the only way I can stay sane and still give a decent answer.
If you need a new number and want it forwarded to your mobile - or any other number - this is what it costs and how to do it using Voipfone. Lots of other companies do it, try Google.
Note: This is traditional telecoms stuff; not VoIP. You dont need a BT line. You dont even need broadband. You only need access to the internet from somewhere to set the service up the first time or change it after that.
This is how it works.
You choose a number and it is held in our network. Calls coming into your number are answered in our network and we divert them out again to the number you have supplied.
You can change the divert number anytime and as often as you like without cost. If you turn the divert off, your calls will go to Voicemail. You voicemail is converted to a sound file and sent by email to you or you can listen to it online (all free).
This is what you do
Its all online, theres no contract, and your number starts working instantly
1. 1.Sign up via the web (its free)
2. Choose your number (see below for types and prices)
3. Put some money on your account its pay-go
4. Set the number you wish to divert to. You can divert to any number, anywhere.
5. Try ringing the new number not from the phone you have set the divert to go to!
Thats it, now anybody calling your new number will now ring your mobile (or whatever number you set). If you hate it or us, cancel without penalty
Diverted calls cost 1p per minute to a UK landline, 1.5p pm to most of the Western world and 12p pm to a UK mobile. We charge by the second with a minimum call charge of 1p.
You can have any kind of number you like (prices are ex VAT):
01 & 02 Geographic - £1.99 per month
The normal, general purpose, everyday telephone number. Geographic numbers show your location; 020 7, 020 8 and now 020 3, is London, 01273 Brighton, 0151 Liverpool etc. (But you can have any location you want now, it doesnt matter where you actually are you dont even need to be in the UK)
Calls to these numbers from BT landlines are charged at 3p per minute (day).
These numbers are universally understood and should be your first choice for a normal businesses number. They are the only type of number that can be reliably dialled from anywhere in the world.
Importantly, 01 and 02 numbers are included as free to dial in mobile contract packages.
0800 Freephone £4.99 per month with an incoming call charge of 2.55p pm
0800 numbers are used for marketing or for sales lines where the strategy is to attract customers to call you. Most people (64%) know they are free to call so they are a good marketing tool. They are often used for short term marketing campaigns; different numbers can be used per advert to help tracking and calculating the relative success of different campaigns.
A major downside is that they are NOT free to call from mobiles and may not be called from outside the UK.
0845 - £1.99 per month
0845 was introduced as a Lo-Call number as callers are charged at local rates (when called from landlines) no matter where they are. Unfortunately, there is no longer a different charge for local and national calls to ordinary geographic numbers so the marketing distinction has been lost.
They are however cheaper to call than geographic numbers 2p rather than 3p pm (day). I doubt that anyone knows this did you?
Ofcom research tells us that they are generally thought to cost the same as dialling 0870.
BT no longer really promote these numbers and they have been undermined by the growth of mobile as they are not included in mobiles inclusive calling minutes and charged for at various rates, always more than a national call. They are often not dial-able from abroad.
0870 Free
Sometime In 2008 these numbers will be killed off by Ofcom, you can still get one but we dont recommend it. If you really need a free number, use 0844.
0844 Free
0844 is a revenue sharing number ie the owner of the number - usually the service provider gets a small proportion of the income generated from the call.
They will normally cost the caller 5p to dial (but there are many rates 5p is the most expensive so most will use that. They are not diallable outside UK and are not included in mobile packages
In a while well be providing an 0844 service which will divert to a landline for free and will include quite a few other free services too.
Meanwhile if you need 0844, email us as we need to set them up manually.
FAQ
What happens if Voipfone goes bust; do I lose my number?
Voipfone is a founder member of ITSPA, the industry trade body. ITSPA has a Code of Practise amongst its members which allows porting between them on request of the customer or in the case of a member ceasing to trade. There are 60 members including, BT, Orange, Tesco, Vonage etc so you number is safe. This is not the case for most other services you will find.
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Highly recommended! 
