The US Federal Communications Commission (FCC) reportedly plans to fine Sprint $105 million for charging customers for unwanted services.

An FCC official confirmed the plan to The Wall Street Journal, and said it relates to the practice of ‘cramming’, in which customers are billed for unwanted services such as text message alerts, horoscopes, sports scores and ringtones.

The fine would be the equal-highest in the watchdog’s history, matched only by the settlement reached with AT&T for similar issues in October. The US Federal Trade Commission also fined T-Mobile US for cramming in July.

A source told Reuters that the Sprint penalty was proposed by FCC chairman Tom Wheeler. When discussing the AT&T case in October, Wheeler said there are “a lot of other carriers involved”.

The investigation is based on a three-month period from August to October 2013, when the regulator said it received close to 35,000 consumer complaints about unwanted charges. The fine is based on the amount of unfair charges believed to have been made by the US number three operator.

The official said customers who believe they have been overcharged by Sprint would be eligible for compensation once the fine is imposed.

They added that three of the five FCC commissioners have indicated they will approve the fine. It isn’t known whether Sprint is in discussions with the regulator about the issue.

The AT&T settlement in October included an $80 million payment to the FTC to cover customer refunds; $20 million in penalties and fees paid to 50 states and the District of Columbia; and $5 million to the FCC.

The T-Mobile case concerned premium SMS services that allegedly swindled customers out of “hundreds of millions of dollars”.

T-Mobile CEO John Legere said the FTC’s move was “sensationalised legal action” and pointed out that the operator scrapped the service last year and was already in the process of reimbursing out-of-pocket customers.

It is believed talks are still taking place to resolve this dispute.