T-Mobile Expanding 3G Footprint

At this point in time, you will rarely see a T-Mobile customer roaming on ATT's network due to no roaming agreements. I'm not entirely sure why the agreements were not renewed. I do remember reading an article about how T-Mobile chose Suncom over ATT but now they own Suncom. I would imagine it's because ATT wanted to charge too much money for those roaming agreements. It's free for customers but someone has to pay those fees and, if ATT is charging too much money, it's not profitable to do that.

...you dont know what you are talking about. Their roaming agreements never disappeared, choosing Suncom over AT&T for roaming doesn't even make sense since Suncom only has a network in the Carolina's and Puerto Rico. GSM networks like T-Mobile and AT&T don't have "in-network" roaming set up like CDMA networks such as Sprint and Verizon do. GSM network set up their roaming agreements on a tower by tower basis. T-Mobile only has roaming agreements where there is no T-Mobile network, dead spots within their network coverage area do not count. Only with Sprint and Verizon will you be roaming within dead spots because of CDMA technology they are not able to set up roaming on a tower by tower basis.

Obviously I'm not referring to areas where Suncom did not have coverage originally. If you have questions about T-Mobile coverage, go do a PCC. Thanks.