AIO Wireless provides coverage all across the US without roaming. They even have service in Puerto Rico. Being owned by AT&T Wireless, they share all the infrastructure (towers) it has to offer.

These are current as of 6/29/2013.

SOURCE: AIO Wireless

Key

Click image for larger version. 

Name:	key.JPG 
Views:	1102 
Size:	10.7 KB 
ID:	18

Continental US

Click image for larger version. 

Name:	continental_us.JPG 
Views:	1415 
Size:	81.1 KB 
ID:	17

Alaska

Click image for larger version. 

Name:	alaska.JPG 
Views:	1253 
Size:	43.7 KB 
ID:	19

Hawaii

Click image for larger version. 

Name:	hawaii.JPG 
Views:	1227 
Size:	22.6 KB 
ID:	20

Puerto Rico

Click image for larger version. 

Name:	puerto_rico.JPG 
Views:	1266 
Size:	28.0 KB 
ID:	21

For an interactive search, you can go to:

Aio Wireless