O2 problem with calls on Philips 535 help!

Posted by chancooluk
Im having problems receiving calls with my new O2 sim card (Which came with my new philips 535), the phone shows that there is signal, (usually full) and network. I can make calls and send messages. But 90% of the time i cannot receive calls or receive my messages, even though the phone shows i have full signal and network on O2 Uk, i have also tried the sim in my siemens A50 and SE T300 but im having the same problems with them. Another thing that occasionally shows up on the philips is "IMSI Failure" wots this? O2 told me that it must be bad coverage in my area, i have been on O2 for 2 years allready with no problems though, o2 customer care are useless. Sorry ive gone on so long, im on "O2 UK PAYG Online Talkalot tariff", can anybody help me?