Massport officials have demanded Uber explain a fee the company tacks onto its fares for rides to and from Logan Airport and to cease referring to it as an “airport surcharge” because customers wrongly believe the charge is levied by Massport.

Uber, which is also the target of a class action suit over the fee, charges $8.75 over and above the fare for rides to and from Logan. The explainer tells customers that “additional charges may apply to your trip in case of tolls, airport surcharges, or other fees related to the trip.” Uber also charges riders $5.25 for the tunnel toll to and from Logan, even though there is no toll on the ride over. In addition, most of Uber’s rides to the airport are in personal vehicles that pay a $3.50 toll.

The letter, dated Sept. 2 from Massport counsel Catherine McDonald, says it is “patently false” for Uber to mislead customers into believing it turns the fee over to the authority. McDonald included in the letter a customer receipt that showed $8.75 for “Logan Massport Surcharge and Toll” as well as a separate charge for the $5.25 toll.

“As you are aware, Massport neither assesses nor requires such a surcharge or toll,” she wrote in the letter which was first reported in the Boston Herald. “Massport requests an immediate explanation from Uber of the charges on its customers’ receipts.”

Uber, in its response, said the receipt Massport attached was old and it had changed the wording last year. The company said the money goes to the driver and is not retained by Uber.

“The airport surcharge was initially listed on receipts as ‘Logan Massport Surcharge & Toll,’” says the letter. “That language was revised in October 2014, at which point receipts displayed the surcharge as ‘Airport Surcharge & Toll.’ The language was later shortened to ‘Airport Surcharge’ beginning in December 2014.”

A spokesman for Massport says despite Uber’s claim to have changed the phrasing, the problems continue to persist.

“Massport has continued to receive complaints even with respect to receipts showing the new wording, as the charge appears to passengers to be assessed by and paid to Massport or the Airport,” Matthew Brelis, Massport’s director of communications wrote in an email. “ We do not want Uber’s language… to create confusion for our customers that it is somehow a fee Massport or the Airport is charging.”

But a spokeswoman for Uber says the company has complied.

“We worked with Massport in the past to change the label of the surcharge in October 2014,” the spokeswoman said. “We remain open and willing to continue these conversations to address any remaining concerns.”

CommonWealth did a report on Uber’s presence at Massport back in August. State regulations say only Boston cabs can pick up at curbside at Logan and only licensed livery vehicles can pick up passengers in other designated areas after paying a one-time $100 fee and then a $3.50 passenger surcharge for each ride from the airport.

Uber’s cheapest service, UberX, is barred from operating at Logan because they are private vehicles but the company works around it by having its higher-priced stable of livery drivers, called UberBlack and UberSUV, respond to requests at Logan but, if requested through the UberX service on the customer’s app, charge the lower price. Uber’s operations at Logan, like elsewhere in the city, has severely cut into the taxi industry’s ridership and revenues.

Uber, Lyft, and other ride-hailing services are currently the focus of dueling legislation at the State House but none of the bills would Massport’s current regulations.