I have an E51 that I use AT&T's service with. I have a N85 on the way. Do I have to go in to the store to activate the phone, or do I just switch the sim card and all that over and I'm good to go? I've only had Verizon in the past so sim cards are new to me. This will be the first time I've switched phones on the AT&T network. Edit: Both are unlocked phones, don't know if that matters.