The convenience store chain is taking the case to court, saying it must compensate customers for the lost time it takes to process a charge on a credit card, which could take up to three days.
A spokeswoman for the company said customers were only charged for two transactions per day and that they did not expect the case could be heard until March.
She said they were considering all options to minimise disruption to customers.
The Irish Times understands the charges would be handled by a credit provider, and customers would be notified of their charges.
However, the case has been brought by the Irish Independent, which reported on the story.