A proposed class action lawsuit has been filed against JPMorgan Chase, alleging that the bank overcharged its credit card customers when they used funds to purchase cryptocurrencies.

Brady Tucker, the plaintiff named in the April 10 complaint, said that Chase Bank incorrectly charged him $143.30 in fees and $20.61 in interest stemming from purchases made using his Chase card in January and February.

Brady is being represented by Finkelstein & Krinsk LLP, a San Diego-based law firm.

The bank was one of a number of institutions to stop allowing its customers to make such purchases using their credit cards at the beginning of February.

According to the complaint, prior to pulling the plug on all purchases, the bank began treating such expenditures as "cash advances" in January, but did so "unbeknownst to Chase's cardholders." Attorneys for the plaintiff alleged that Chase Bank violated the Truth in Lending Act by not disclosing the policy shift.

"The complete lack of fair notice to Chase's cardholders caused them to unknowingly incur millions of dollars in cash advance fees and sky-high interest charges on each and every crypto purchase," the complaint says. Chase did not charge debit card users similar fees.

The plaintiff's lawyers – who are seeking the return of the fees as well as "additional statutory damages in the aggregate amount of $1 million" – are seeking class-action status. While the complaint says that the size of the class cannot be determined prior to discovery, it argues that this group likely consists of "hundreds or thousands of members."

A representative for JPMorgan Chase declined to comment when reached.

JPMorgan Chase image via Shutterstock.