Stuck with a brand new faulty phone!!!

I bought a Samsung A30 for my younger brother at Markham in Musina. It turns out the selfie camera was not working at all. We took the phone back to the store and were told that it was out of the free 7 day exchange by 1 day. The lady at the store took the phone back to the supplier to fix the problem only to return with a faulty back camera. They had told us that they would give us a new phone should it fail to be fixed. The phone was checked and the damage was not due to negligence. It was a factory fault!! My brother went to fetch the phone a few days ago and he was told that there is nothiing the store can do unless he pays money for them to return it and fix it again. Now he is using a faulty new phone as it is going to be expensive for us to pay for them to fix the camera. R4000 gone too waste!! I regret purchasing the phone from Markhams.