The Co-operative's supermarket arm said today it has refunded customers after a processing error means customers who bought groceries or used a filling station using a credit or debit card were charged twice.
In a statement today, the company admitted the error, which affects customers who shopped at its stores on 7 July, but said refunds would be made directly to customers' accounts within 24 hours.
"We will also reimburse any customers who have incurred bank charges as a result of this error," it assured customers, asking them to contact its customer careline on 0800 068 6727.
The Co-op has undergone a management shake-up in recent months, ditching its 22-strong board of members last April, in favour of a non-executive board and a 100-strong member council to nominate directors.
Last month it waded into the supermarket price war, introducing 39p veg (including iceberg lettuces, cucumbers and carrots), and slashing the price of eggs, chicken, bacon and bread.
It's also planning to open 100 new convenience stores across the UK.
"Consumers are shopping differently, buying little, more frequently," said Steve Murrells, its retail chief executive, back in June.