Diners Club not paying out OUR CR amount

We had been saving money for the past few months to spend on our recent holiday in London. I did everything right including advising Diners Club where I would be. They omitted to let me know that Diners Club card is not accepted everywhere in London. Our card was not accepted at any point in Zone 1 London, not a restaurant or any other shop. We luckily had backup, so we used our backup card. However, the credit was in my Diners Club account. On arrival I immediately requested that this Credit amount be transferred to my backup card or my account. This is when all the runaround began. First they needed confirmation that I had indeed paid in the money, which with some reservation I sent to them. Then they needed confirmation of the account that had made the payments, which I also sent to them. Two weeks later, still not payment. This my credit not theirs, its my savings, not their money. I could understand if i was borrowing money from them, but this is not the case.