The FCC announced that AT&T will pay a $700,000 fine and return money to customers who paid excessive charges after they were unknowingly switched to a costlier data plan, IntoMobile reports.

The fine stemmed from a series of complaints from AT&T customers who were switched to a more expensive monthly data plan without their consent.

According to the complaint, customers were switched from a pay-as-you-go plan to a monthly subscription due to a mistake by AT&T. The error was discovered in 2010 and customers were reimbursed when they contacted the carrier about the overage. AT&T says this glitch affected less than 0.03 percent of its customers. As part of the FCC’s settlement, AT&T will reimburse effected customers by paying them the $25 to $30 extra they paid each month. If customers believe they are eligible for a refund, they can contact AT&T.

The carrier will also search its own database to find and contact those customers who are owed a refund.