In that case.. if you have service and the phone won't load pages, then yes, it is AT&T.. I haven't had that problem. If your phone is having reception issues (while your others didn't).. Then there is no way you can blame AT&T. That is Apple. AT&T has always worked great for me as far as reception goes. Yeah, if I go into a rural area, I am gonna lose some reception, but there isn't a carrier out there who covers everywhere. When you find it, let me know.
BTW.. A friend of mine has Verizon and his internet is slower than AT&T. So don't always think that Verizon is the answer.