You must get a phone compatible with the AT@T network. Usually from an approved dealer.
I had AT@T about 10 years ago. Their service sucked about as much as the $700 for a phone and another $150 for a rebuild a little over a year later did. I know! All of them have improved, but the bad taste!:disgust:
I just got 2 Sprint PCS phones. They have a far better plan than any other provider. I'm in a fringe area for them, yet reception is crystal clear!
I got a Qualcomm 2035. It has more features that I'll ever use includeing E-Mail and web access. 2.5 cents a minute makes it cheaper than my landline! Btw, I got the Sprint PCS as much to use locally as in other parts of the country. In the small town I live in it is long distance to call out of the city limits! Even on AT@T's best long distance rate, 5 cents a minute for interstate and 7 for intrastate is the best plan I can find.
After considerable online research, I found the local Best Buy had the best deals on phones regardless the provider.
After various rebates they were free as were the hands-free accessories.
If you are 'stuck' with AT@T, you must get a phone that is ready for their service. My Sprint PCS phones can access the AT@T network by roaming, but at a high cost.