Awful Service from RARC - Exchanging Car Parts

I'm writing this to share the bad experience and awful service I received from Roodepoort Accident Repair Centre. My car was with them for repair from early February after I was involved in a car accident. The repaired my car and I collected the car, after a month collected my car, the started giving me issues with the battery. I booked the car in for a service at my local Audi dealership after it gave me an engine fault warning light and upon diagnostic the car, the dealership picked up that the battery fitted in my car was not an original Audi battery that the very same dealership changed last year December. I then called RARC to enquire about it, I spoke to Wikus and strangely he never denied instead he promised to change the battery. However he couldn’t give me reasons why they exchanged the battery and put an old dead battery. On Thursday the 20th I took the car to the Audi dealership, since RARC promised to pay for the battery and I sent the invoice with dealership’s banking details. Since then they haven’t make any payment, my car is still with the dealership and the dealership is complaining for space. I tried to reached out to Wikus from RARC again and he promised to get back to me and still giving me run around. I sent him several whatsapp messages which he read and never responded. I’m of the view that this is what RARC do by swapping parts and replace them with old parts when customers vehicles are under their watch for repairs. I reached out to my insurer to inform them of the incident and my insurer unable to get hold of Wikus. Help desk transferred calls to him and he’s not taking their calls. This is sickening that they treat their valued assets (customers) this way but exchanging parts or tyres and most probably customers don’t get to notice this when they pick up their cars or don’t check or have knowledge about cars to noticed if part where changed in their cars.