Wells Fargo has already admitted to charging people for overdrawing bank accounts that they didn't have and for car insurance that they didn't need. Now, it's being accused of ripping off vulnerable mom-and-pop businesses.

For several years, Wells Fargo's merchant services division overcharged small businesses for processing credit card transactions, a lawsuit alleges. Business owners who tried to leave Wells Fargo were charged "massive early termination fees," according to the lawsuit filed in US District Court.

The "overbilling scheme" targeted less sophisticated businesses by using "deceptive language" in a 63-page contract designed to confuse them, the lawsuit filed on August 4 claims. The lawyer filed court documents to seek class action status.

The latest controversy centers on Wells Fargo Merchant Services, a joint venture that is 60% owned by Wells Fargo and 40% controlled by First Data (FDC).

A former employee of the Wells Fargo (WFC) business told CNNMoney that he was instructed to target these small businesses.

"We used to be told to go out and club the baby seals: mom-pop-shops that had no legal support," he said in an interview. The former Wells Fargo employee spoke on the condition of anonymity, but CNNMoney verified that he worked for Wells Fargo Merchant Services.

The former Wells Fargo employee told CNNMoney that when he worked there, from 2011 to 2013, it was nearly impossible for business owners to leave the merchant agreement. "God would have had a hard time" escaping the contract, he said. "It really was like a shady used car deal."

Related: Wells Fargo customer: It felt like my car was held as extortion

One of the plaintiffs in the suit, Queen City Tours, claims it was assessed a $500 early termination fee after trying to leave Wells Fargo Merchant Services.

The North Carolina company, which focuses on African-American themed tours in Charlotte and is owned by military veteran Juan Whipple, alleges in the lawsuit that Wells Fargo charged it monthly fees of $20 to $35 for failing to have a minimum number of transactions. That's despite the fact that the company claims the contract said there would be no such fees. The tour company says in the lawsuit that its business is seasonal, and that it has few sales during off-peak months.

The second plaintiff, the Pennsylvania restaurant Patti's Pitas, claims it was "pounded by excessive fees" -- even after it went out of business in May 2017. When Patti's Pitas tried to leave the contract, it was told it couldn't because of a three-year term that the owner wasn't aware of, the lawsuit said. Wells Fargo, which was already under heavy legal scrutiny regarding unauthorized bank and credit card accounts, eventually closed the account without a termination fee.

Regarding the lawsuit, the bank said, "We deny these claims and intend to defend against [it]." The company added that it believes its "negotiated pricing terms are fair and were administrated appropriately."

Wells Fargo declined to respond to the specific claims by the former employee.

First Data also declined to comment to CNNMoney.

Related: Wells Fargo is once again in hot water

The overbilling allegations are the latest black eye for Wells Fargo. Nearly a year ago, the bank admitted it created some two million potentially unauthorized bank and credit card accounts. Wells Fargo recently said an ongoing review of earlier accounts is likely to reveal many more fake accounts.

Wells Fargo has taken countless steps to try to fix its broken culture, including reforming the unrealistic sales goals that were at the heart of the scandal. The bank has also replaced its senior management and conducted an exhaustive internal investigation that uncovered red flags going back to 2004.

But Wells Fargo has landed back in hot water in recent weeks. Late last month, the company said it charged as many as 570,000 customers for car insurance they didn't need. About 20,000 of those customers may have had their vehicles repossessed in part because of those unnecessary insurance costs.

Wells Fargo has apologized for the auto insurance fiasco and promised to refund those customers affected. A New York regulator subpoenaed two Wells Fargo divisions last week demanding the bank turn over loan agreements and other documents, a person familiar with the matter told CNNMoney.

Samir Hanef, a clinical social worker from North Carolina, is one of the Wells Fargo customers who had his car repossessed.

"I was forced to pay for Wells Fargo's mistake," Hanef told CNNMoney.