WeFix Mall of Africa Broke my iPhone X camera and caused serial number mismatch

I booked my fully functional iPhone X to WeFix mall of Africa for back cover replacement on 11th August. Job Card: MAPH210320. The replacement cover is R6000 which I have already paid cash. The phone was silver. They replaced it with a black cover. When I collected the phone the camera was no longer working. Old story of theirs they now claim it means it was not working before I brought it but I know it was. I took it to iStore to have the screen replaced as I have iCare as the screen also needed replacement. iStore mentioned that the phone has a 'serial number mismatch' and they could not work on it as it is no longer the phone I purchased from them. This makes it clear that the reason the camera does not work anymore is because the parts of the phone have been changed and replaced with other parts that don't work. I went more than 5 times to WeFix to try get this issue of the camera resolved and at some point they told me they can take another camera from another phone and replace. And also they further told me they can give me a screen for R2700 as iStore won't work on a serial number mismatch phone. I no longer want to work with these guys as I have had to buy a new phone already which cost me R6000 as I cannot be without a phone for 2 weeks as I work with the phone. This means so far I have spent R12000 and these guys refuse to refund my money. I requested that they put back my old silver parts and take they black cover and refund me. I was advised at mall of africa WeFix that it's a waste of time as WeFix head office will refuse to refund me they will rather try find a loophole than refund. I filled the form anyway and am waiting for a response from the head office. It's day 1. Should I not get my money back it will be clear that WeFix are *****s because I no longer want their parts as they broke my phone and caused serial number mismatch with iStore. I want my money back and I am no longer interested in business with WeFix Mall of Africa. I have been without a phone for 2 weeks I had to buy one so I no longer need them to waste my time any longer. I regret even setting my foot there.