Discovery systems at fault but no refund

I have signed up with Discovery Insure and as part of that I have a Vitality Drive card.<br> Based on my fuel purchases at BP, Discovery promised me cash back.<br> After a couple of months, I noticed that no fuel purchases were being registered.<br> I contacted Discovery and they acknowledged that they had made a mistake.<br> They asked for my fuel slips so they could capture the purchases manually.<br> I informed them that I do not keep fuel slips but that I would submit statements for my fuel card that clearly states the relevant purchases.<br> This was agreed to by the Staff member I spoke to.<br> Subsequent to this, Discovery is now refusing to refund me money based on the statements. They refer to T&C that states only slips can be used.<br> This even though Discovery has acknowledged that they are the cause of the fuel purchases not being captured correctly.