First Car Rental nightmare

On the 18th September we flew to George to visist some family. At the First rental counter I was informed that the rental deposit of R 18 000 is required. After a scuffle around this we gave in and paid. I have NOT received R 15 000 back - only R 2885 WHAT is the reason?? Why are you not paying me back?? AVIS is expensive - but painless. I will be returning to AVIS