Refund of a credit not possible after a year

I have a credit with Rubicon for over a year now. I have asked for a refund over a year ago. I drove to Rubicon with the card I used to pay with and they refused a refund. They then asked for documents like proof of bank account of the same account and I send that. Then when I asked again after a year they needed more documentation. I send it again but still no refund. Most of the time that I phone I don't even get through to the accounts department. I leave a message and then no reply. Even escalating it to the operational manager who is now ignoring my calls.