Double Billed and System Offline

A car was hired on 16 November and rental was paid online. When the car was collected, another card was used for the deposit. Dollar then said they will take the rental from that new card. From the 18 November, we have been calling to get them to reverse the hold on the first card and the agents keep on saying SYSTEM IS OFFLINE. Take note, on 3 occassions, details were taken and I was promised a call back. The first person who promised such even disputed that the rental was 1 day, I had proof that it was 1 day as there is also a boarding pass. The agents are also not so helpful.