I'm at my wits end trying to use my unlocked Iphone 4s.

I have been trying to figure this one out for the last week but to no avail.

I have an iphone 4s that is unlocked, it accepts any sim, when I switch the phone on to set it up it shows my network and full coverage but once I try to create an icloud id and get passed the initial setup my coverage bars drop to zero(carrier name is still there)

I have tried updating the iOS and itunes and performing a factory reset but this isn't fixing the issue at all.

Please any help would be much appreciated as I don't think I've ever been more frustrated with an in-animate object, it's on a very fast collision course with my wall unless the issue is resolved soon.