Foschini broke a phone that is still under warranty and still wants us to pay for it

My Aunt bought my little sister a cellphone at Foschini Kroonstad about two months ago and we have been bringing back the phone for fixing ever since. The first time we were told that the phone was fixed of which it only worked for two weeks and gave her the same problem again. we took it back as it is still under warranty, we were told it will be back within a week, but it actually took four weeks to be brought back, when we went to get the phone at the store they brought it back not fixed and now with even a cracked screen mind you when we took it to the store for fixing the screen was still fine. As we refused to take back the phone like that the sales consultant told us we had no choice as it wont be fixed, this is a phone that my Aunt still pays for till date. Came in new with a software problem, but was brought back with the actual problem not fixed and now an extra problem of a terribly cracked screen. We are uterly disgusted by the bad service we got from Foschini and will completely not allow my aunt to pay for a phone that was sold with problems and can't function. The phone model is a Samsung J4 Core Black, the account holder is Maoke ML account number ***.