"We have retained a nationally recognized cyber fraud expert team to investigate," AT&T said in a statement. "Jawa has agreed to cooperate by allowing these independent investigators full access to data and records. In the interim, we have suspended the short codes identified in the complaint, and have identified and suspended additional related short codes."

The codes are short phone numbers that users send a text to in order to sign up for messages with information such as sports scores, recipes and movie times. The codes are administered by the CTIA mobile trade group so that they will work across operators.

T-Mobile did not reply to a question about whether it was looking into Jawa. Sprint said it has not initiated any litigation against the company.

Verizon has had trouble with the owners of Jawa in the past. The operator said it first discovered that a company called Cylon, owned by the CEO of Jawa, Jason Hope, wasn't complying with Verizon's terms for offering premium text services. As a result, Verizon suspended Cylon.

However, Verizon said Hope and his partner came up with a way around the suspension. They set up a new company each time they leased a short code and launched a campaign so that the operator didn't know the campaign was affiliated with Hope, Verizon alleges.