Avis has not refunded me

I rented an Avis car through Discovery Insure on 20 January and returned the car 24 January. To date, despite several calls, I have not been refunded my deposit of around R2500. Each time I call, I'm told either that the file has not been finalized, or that the problem lies with Discovery Insure who is delaying the refund. I've been promised on three separate calls to expect a refund within 2-3 working days. But still no refund.. On the day I returned the car, I was told I had damaged the bumper. This damage was specified on the checklist before I took the car. It was only when I told Avis I would resort to social media if they charged me for the damage, that they wrote that they would not charge me for the damage. But I still have not received my deposit back.