can't make calls or sms on iphone 3gs after iOs5 upgrade?

I upgraded to iOS5 on my iphone 3gs and I am having major problems connecting to the 3g network. I can't make or recieve calls or sms, or log on to the internet over the 3g network. wifi works fine, but that doesn't help with the calls or the sms, and i can't always be on wifi for my emails. the phone worked fine before the upgrade.

i've restored the entire phone as a new phone, i've gone in to the apple store and had my phone looked at, they say there's nothing wrong with the hardware.

i live in Canada and my carrier is Rogers - of course when I call them for help they say it must be the phone not their network. they'd rather i buy a new phone and sign another 3 year contract

the only thing that seems to help is restoring network settings. immediately after doing that I can make calls, send and receive sms, and use the internet over 3g. but it only fixes it temporarily... after about 15 mins I'm back to the same problem. can't make or receive call etc.

anyone else having this same problem?

anyone know of a solution?