The Washington State Attorney General's office has gone after the big cellphone company over deceptive practices.

If you're a T-Mobile customer, you could have a refund coming. Janet Guthrie of the AG's office announced today a settlement was reached with the cellphone company over deceptive advertising. After receiving a number of complaints, the office launched an investigation into the T-Mobile plan.

Guthrie said the company was running ads that promised consumers no annual contracts, but actually contained hidden charges for early termination of the plans. According to information released today:

T-Mobile recently launched a new type of wireless service plan, claiming to offer 'no restrictions,' 'no annual contract' and no requirement that the consumer 'serve a two-year sentence.' However, this new plan does not include a phone. Instead, the company provides the option for consumers to purchase a phone at a monthly rate over a two-year term. They also offer the opportunity to bring your own phone or pay the entire cost of the phone up front. After an investigation of the company’s practices, the Attorney General’s Office learned that the company failed to disclose that customers who purchase a phone using the 24-month payment plan must carry a wireless service agreement with T-Mobile for the entire 24 months— or pay the full balance owed on phone if they cancel earlier."

The company agreed to stop running ads that did not disclose the additional fees.

Guthrie also said in the press release:

All consumers who purchased T-Mobile service and equipment between March 26 and April 25, 2013, may obtain a full refund for their telephone equipment and cancel their service plans without being required to pay the remaining balance owed on their devices — as long as the customer cancels his or her service per the terms of the agreement."

Customers can contact T-Moble by calling 877-746-0909 or 611 from their T-Mobile phone. T-Mobile will also pay over $26,000 in attorney fees and court costs to the Washington State Attorney General's office as part of the settlement.