I was on orange uk - I had this problem with Nokia N97, Blackberry Curve and Xperia X10i
I've talked nicely to orange, yelled at them, threatened and begged, and after trying several permutations of getting a half decent signal with them under their advice, i just gave up - there will be no recourse with them, no chance of getting out of your contract unless you pay your way out of it. It's a disgraceful service.
I was told by one orange customer service rep that texts to my phone seem to be disappearing into a black hole, but they should get sent through eventually. 6 hours later i received over 30 text messages, 2 of which were very important, and this happened many many times, what can i say, my blood pressure hit the roof .... too much to bear .... i slung my sim card in a drawer and took out another contract with another operator, so yes, i'm paying