T-Mobile claims its customers have a better roaming experience in South Africa than they do on AT&T’s network in South Dakota. The carrier says its customers got speeds twice as fast and unlimited data in South Africa.

In an FCC filing posted Friday, T-Mobile attributes to the audacious factoid to AT&T’s “artificially high roaming rates.”

T-Mobile is urging the FCC to expedite its actions in providing guidance and criteria for “commercially reasonable” data roaming rates in accordance with the 2011 Data Roaming Order. The carrier says faster reaction from the Commission is needed as many legacy roaming agreements are giving way to new LTE roaming agreements.

T-Mobile says it is not seeking the regulation of rates but rather requesting guidance to “facilitate negotiation of commercial agreements and dispute resolution.”

Responding to T-Mobile’s petition in a blog post, AT&T Vice President of Regulatory Joan Marsh said T-Mobile’s request is “unlawful” and in violation of the Telecommunications Act and would “push the Commission’s regime over the line into impermissible common carrier regulation.”

T-Mobile says its current data roaming rate with AT&T is 150 percent higher than the average domestic roaming rate the carrier currently pays.