Menlyn istore damaged my phone

I took my phone to Menlyn store to be updated and the lady(Thato) who assisted me failed to do a diagnostic test to check why the phone was not updating. As a result the phone broke down because it had underlying issues and that would have been discovered before she attempted to update it. Now they are saying I am liable to pay R12000 to fix the phone while it was working completely fine when I entered the shop and it was damaged by their *********** employee. I feel like this matter is handled in this manner because I am black had it been a white person they would have long fixed or replaced the phone. I tried contacting the manager and received a call from the assistant manager who dropped the call on me while I was still talking . This is another thing that aggravates me because I am not receiving any help and not having a phone is inconveniencing me a lot.