Q: I bought my iphone 4 in the UK and I am trying to use a sim in the UAE and it doesn't work.  It says that the sim is not valid, how can I get this unlocked?

Your provider in the UK will have to unlock the phone.

You are saying the phone is locked, but then you are saying there is no provider. The two situations cannot peacefully coexist. Contact Apple and they can tell you if the phone is locked and if locked to which provider the phone is locked. People on this board are not Apple employees and cannot get you that information.

If you bought it from the Apple Store it would have been unlocked. There may be a problem with the SIM instead? Have you tried another SIM or contacted the SIM's cell provider to see if they can help?