Overcharged on excess and still awaiting refund

I have been a client since 2012. In 2019 I was involved in an accident where a taxi driver bumped my car. My excess was R1500, but I was told to fork out R5000 instead (and they will deal with the third party), they would then refund me the R3500 difference. This was very odd to me and to this day I am still waiting for that R3500, two years later.