Cryptocurrency exchange and wallet Coinbase blamed Visa for an issue that saw some users experience unauthorized money withdrawals, but the card service said it wasn't at fault.
Coinbase users can link a credit or debit card to Coinbase and buy cryptocurrency immediately. Some users had been noticing that there were duplicate charges when they executed a transaction. In some cases, this drained their bank account to zero and even caused them to be charged overdraft fees.
On Thursday, Coinbase released a statement in a series of tweets in which it said Visa was to blame for the problem.
Coinbase explained that large banks and card issuers had requested that card networks change the merchant category code for the purchase of digital currency. The change of code would allow large banks and card issuers to charge additional fees on transactions to buy cryptocurrencies.
The digital currency service said it is working with major card networks to create a new code for cryptocurrencies.
But Visa said that it has not made any changes that would result in customers seeing duplicate transactions.
"Visa has not made any systems changes that would result in the duplicate transactions cardholders are reporting. We are also not aware of any other merchants who are experiencing this issue," the company said in an emailed statement to CNBC Friday.
"We are reaching out to this merchant's acquiring financial institution to offer assistance and to ensure cardholders are protected from unauthorized transactions."
After a crash in the cryptocurrency market earlier this month, bitcoin and other cryptocurrencies have recovered slightly. Bitcoin jumped above the $10,000 mark for the first time in two weeks on Thursday.