Cellphone repair services pathetic

Cellphone repair services pathetic. Bought a IPhone 6 on the 17th May 2019. Worked for about 2 months then stopped reading the card. Cellphone was send in 3 x times for repairs just to receive it back again, same issue. According to the cellphone repairs company Foschini use they said that the phone must come back 3 x for repairs before it will be replaced which I think is unacceptable because I must pay for something I don't have any use of. They also confirmed that another network card was tested on the phone and it worked. We tested this handset with different network cards and nothing worked. I requested that I want the money be credited back to my account as I really don't want this product any more. According to the store they can't reverse the transaction. I want the transaction reversed please. Can't see why you have to buy something and when you are not happy with the service or product you can't get your money back. Please resolve this issue.