Refund of Deposit

Rented a VW Polo last year with a R7000 deposit. Somebody smashed the back side window. This was signed for me and tempest person checking car in. "Smashed back left door window". Tempest is demanding I pay them R11 000. It took 6 months to get the proof which ended up being damages for another car - Suzuki Swift returned by a Roy. I cant get hold of anyone to assist me and when i phone them i get told they will get back to me. Total incompetence. Just don't know anymore what to do to get my money back.