AT&T (News - Alert) will refund money to customers and pay the federal government another $700,000 in fines after the company mistakenly billed a small number of smartphone users for monthly data plans, news reports said.

The Associated Press said the requirement was a mistake and did not apply if subscribers got a new phone under insurance or warranty, or moved to a different service area.

These customers got placed on monthly plans due to computer errors, The AP said.

The refunds could total up to $30 a month, according to the FCC (News - Alert). Customers who got in touch with AT&T already got refunds.

Smartphone customers without a plan or using a pay-per-use plan were supposed to sign up for a plan if they upgraded to a new smartphone, according to Web RTC World. But AT&T improperly charged some of them despite a promise to the contrary.

“Today’s action sends a clear signal that wireless carriers can’t wrongfully charge consumers,” FCC Chairman Julius Genachowski (News - Alert) said in a statement quoted by RedOrbit. “These strong FCC accountability measures will ensure customers are not over-charged. I am pleased that AT&T is taking the appropriate steps to resolve this issue.”

Also, AT&T has to train customer reps on the issue and send compliance reports to the FCC, RedOrbit said. The mistake only impacted a small number of AT&T subscribers.

“Based on a review of our refund process, we believe a vast majority of those customers affected by the billing error have already been made whole,” company spokesman Marty Richter, told CNET. "But as part of the decree we'll be providing a bill-page notice to affected customers, offering refunds, and giving them the option to return to a data pay-per-use plan, or to have a data block applied to their phone."