Data roaming is probably something that many customers never notice, but rest assured that the practice still exists. Data allotments are shared between carriers more times than one might think so that carriers can make sure that their customers are connected as much as possible, even when not technically connected to towers that belong to their own network. Recently there has been some issues over the business practices of data roaming between T-Mobile and AT&T, with AT&T stating that they buy more in data roaming than they sell. T-Mobile believes this not to be true of course and have issued some responses to the FCC about AT&T's claims.
The response was issued by T-Mobile's Senior VP of Government affairs, Andrew Levin, who mentions that T-Mobile had sent more than 2,000 times the volume of data traffic to AT&T than it received from them. The reason this is an issue for T-Mobile is because AT&T has a much larger footprint, so they and their customers have the capacity to be less affected by data roaming costs. Because of this AT&T can keep their roaming rates high, which forces other smaller carriers, like T-Mobile, to account for these costs and raise their rates, as well as throttle and cap out their customers to keep from losing profit, which in the end causes an imbalance to the data traffic.
T-Mobile also takes issue with AT&T's claim that they offer T-Mobile a data roaming rate of $0.18 per MB, because AT&T has qualification requirements set in place to meet that price which T-Mobile states they rarely qualify for due to the way that AT&T has things set up, making the price per MB more false than true. Last year T-Mobile started petitions to convince the FCC to take another look at the 2011 data roaming order which saw carriers offer a reasonable cost for data roaming on their networks. T-Mobile's efforts seek to get the FCC to issue new guidance and enforcement requirements on data roaming, while AT&T has issued a response of their own stating that should the FCC revisit the initial terms set in 2011, it would cause the FCC to have to come up with a new set of rules while also contradicting their original terms.