this was originally posted by bbcn, I thought I should also put it here, this is important:
These +4470 numbers are a gift to online scammers by British phone regulators. They are primarily owned by obscure British phone companies offering an anonymous call forwarding service. The economic model of these services is simple: The caller dials a rather expensive UK number and the UK service provider forwards the incoming call to a somewhat less expensive to call international number (for example a Nigerian mobile phone, which remains hidden from the caller), pocketing the difference between the call rates. For example, the caller might pay 50 cents per minute to call a +44 70 number and the call will then be forwarded to a Nigerian mobile phone that costs 25 cents per minute, leaving 25 cents per minute as a net margin for the service operator. The more successful the scammers are, the more money the phone company makes. Whoever said crime doesn’t pay?
These UK phone numbers are very attractive to scammers: When people can be made to believe that they are dealing with a bank, lawyer or government official in London, UK when they’re actually talking to a scammer on his cell phone in an Internet cafe in Lagos, Nigeria then they are much more easily defrauded by criminals.
As far as I can tell these numbers aren’t really being used for any other purpose than to enable international online crimes to be committed. In some nine years of tracking Nigerian scam emails, I have yet to come across a single legitimate user of a +44 70 number. I really don’t understand why the British government has allowed those services to continue to operate.