Hypothetical then - let's say I agree to repay the amount. Is there anything that states how much the minimum repayments have to be? I'm thinking of stringing it out for the same length of time it took them to get in touch with me.

Hi, First time post here, but given the nature of what is going on I could really do with some advice. So this all relates to a refund they gave my partner and I some 2.5 to 3 years ago. At that point we were living in a one bedroom flat with a prepayment meter. Now, according to nPower, due to a mistake on their side (they said over charging) we were to be refunded £500. Upon receipt of the refund letter my partner phoned nPower customer services to ensure it was genuine and it wasn't being handed out in error. We were re-assured it was genuine and that we were definitely owed the money. Flash forward to yesterday where one of their lovely threat letters was dropped onto my doormat in our new house. This letter stated that we owe £429 due to unpaid charges (from 2.5-3 years go!), with £7 of that being a trace charge as we hadn't provided our new address to them (we left nPower about 6 months before we moved house and went with another provider and ceased to be a customer, therefore no need to inform them of anything). Now, according to nPower, the money they refunded was correct, however, as the money really should have gone into the pre-payment account and not the standard tariff account we have taken £500 from them and not paid for our gas and lecky which was used under the pre-payment account. I understand the issue they are having, but I fail to see how after 3 years they can try to claim we owe this money. It is simply their error, and their mistake, and I feel a time frame of 3 years is far to long to try and be claiming money for debts we never accrued from non-payment. We have never not paid for our electricity or gas! What should I do with this? They are now wanting to escalate it to further with the view to get the bailiffs in.