I just purchased an unlocked 7290 here in the US, and will be using it in the UK, and need a SIM card to purchase for pay as you go, prepaid. I only need to make phone calls and receive phone calls. I'm sort of lost - I've searched in the forums and don't know what to buy. Or where to buy it from! I don't need to sign up with a plan if all I am doing is making and receiving calls and don't need any other functions, correct?

Thanks in advance!

If you dont intend to use it for aything except phone calls then any SIM will work from a local UK carrier. You will need a blackberry data plan if you go beyond that.