New York City officials filed a lawsuit against T-Mobile US, accusing the operator of engaging in a variety of deceptive sales practices.

Officials said in a press release the action is the culmination of a year-long investigation by the city’s Department of Consumer and Worker Protection (DCWP).

Specifically, the lawsuit alleges 56 corporate and authorised dealers for the operator and its Metro by T-Mobile prepaid subsidiary tricked people into buying used phones; enrolled customers in financing plans without their consent; charged illegal taxes, mystery fees and sums for unwanted services; and deceived consumers about its refund policy.

The action tallies more than 2,200 violations in total.

Consumers with limited financial resources or a poor credit history were especially vulnerable to these tactics, officials claimed.

DCWP Commissioner Lorelei Salas said: “T-Mobile’s rampant and repeated deception is made more troubling by the fact that these tactics particularly harm consumers who are simply seeking to find an affordable wireless plan.”

A T-Mobile representative told The Wall Street Journal the operator takes the allegations seriously and is investigating. The representative said while it can’t yet comment on specifics, the claims are “completely at odds with the integrity of our team and the commitment they have to taking care of our customers every day”.

City officials want T-Mobile to transfer revenue made from such schemes into a compensation fund for victims, help restore the credit scores of affected customers and pay civil penalties.