I believe this is a number you can call from the UK which allows cheap calls to the US. I'm not sure of the name of the company that provides this service though. Once you dial this number from the UK you can then enter the US phone number you want to dial and you get charged less than dialling from your own phone. The recipent sees the 77-4436-9900 number on their caller ID. It looks as though someone is abusing this service. Mean, fraudulent poeple exist - it's part of life. Please do not be stupid enough to give out your details to a random stranger.
Marie you are exactly right. Someone calls me from the UK on a cell phone and each time she calls it is this same number 774 436-9900 showing up on my caller id, which is not at all her cell phone number. Must be some sort of calling card that she routes the calls through to pay less money to call the US.