Europcar overcharged me TWICE, & still have not contacted me!

I booked a Europcar via kulula.com (linked to my Kulula flight) for the 10th of December 2019 and I paid for the car in full, in advance, via the Kulula website using my credit card. It gave me the booking reference number ENM9APA. When I collect the car on the 10th of December at Lanseria a R3000 holding charge was levied on my card as is the norm for potential damages/fuel/tolls. This was supposed to be credited back to me when I returned the car on the stipulated return date, less any fuel and toll charges (as there was no damage). When checking my credit card statement I noticed that Europcar had incorrectly refunded me on the 17th of December a much lesser amount (not the correct one. I logged a query with their call centre and they advised that Lanseria had incorrectly charged me for an extra day, later return, which was an error on their side (as I flew out on Kulula from Lanseria 1 hour after returning the car on time). I was given a query reference number of 551608 on the 18th of December and advised via email that it would be resolved in 3 to 5 working days. I did not receive any email resolving that query reference nor did I receive any calls to resolve their overcharging, instead all that happened is on the 31st of December they charged my credit card even more money instead of refunding me for the incorrect overcharges. Not a very good reflection on Europcar and I certainly won’t be trusting them again in future. Let’s see if this listing on HelloPeter will help them to improve their Customer comm’s by resolving their own query reference numbers via proper email &/or telephone call