Mexico City - A Mexican court has ruled against the domestic business of wireless operator Nextel, ordering it to compensate around 3 million customers for improper charges since 2012, the Profeco consumer protection agency said.

Profeco, which brought the class-action lawsuit on behalf of the affected customers, called the Mexico City-based tribunal's ruling "historic."

The suit was filed against Nextel over a range of alleged improper charges, including ones for "services that were not delivered, deficient or whose characteristics and content differed from the plans or packages offered."

Nextel must reimburse customers for the improper charges, with those payments subject to a 9 percent annual interest rate. The affected customers also will receive additional compensation equivalent to 20 percent of their losses.

Affected customers must show proof that they received services from Nextel between 2012 and the conclusion of the trial that did not meet the conditions, quality and characteristics offered.

Profeco chief Rafael Ochoa Morales said the sentence was the agency's first favorable ruling in a class-action consumer lawsuit since it began bringing these cases in 2013 and therefore "sets an important precedent."

U.S. telecommunications giant AT&T said in January 2015 that it had agreed to acquire Nextel Mexico from NII Holdings for around $1.88 billion, making the announcement just a few days after closing its acquisition of Mexican wireless operator Iusacell for $2.5 billion.