E.ON's customer service director, David Bird, said:
We are very sorry to have let down some of our former customers and have made clear that we will refund the money plus interest. Our systems are being updated to ensure this mistake can never happen again.
We've been open in our failure with the energy regulator, Ofgem, and are pleased to have agreed with them how we can put this right and have identified all customers who are due to receive payment from us in January.
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