Help?! If I buy a phone here, and ship it to my boyfriend will the coverage be the same?

I am currently planning on buying a cell phone for my boyfriend, and adding him to my AT%26amp;T family plan, but there's one problem... He lives in new york and I am in oklahoma, I looked at the AT%26amp;T map and where he's at there's plenty of coverage, but I'm just nervous and not sure about if there's roaming? or what might happen, or if there would be any difference if he was to use it up there rather than down here? We realize that he can't get the area code up there, it would have to be the area code here because I will be activating it here, Anything that anyone could let me know about I'd greatly appreciate it, I'm just trying to cover all bases, Best answer will be given, Thanks! =)Help?! If I buy a phone here, and ship it to my boyfriend will the coverage be the same?
From what I understand AT%26amp;T gets absolutely horrible service in NY...especially NYC.