SIM Card Trouble!

I recently bought an iPhone 4 and went to my carrier (Rogers) to activate a new SIM but it kept on saying no service. I've tried restoring, restarting and even another SIM card but it's still saying no service! They said that it had something to do with the phone. Everything else works perfectly and this phone is not unlocked nor jailbroken, I'm just wondering if this problem is fixable or do I have to get a new phone? Please someone help!!