Ackermans don't want to refund me.

I bought a cell phone at ackermans groblersdal in December 2024 and the phone had a problem of switching off and not charging again. I have return the phone at the shop more than 3 times with the same problem. My last return they said if the problem persists they will take it back and refund me, it's been two months but my phone is still with them. What pains is that no feedback received from them and when I go to the shops they are telling me different stories. The warranty of the phone expires in December and I think they are just buying time for the warranty to expire so they don't refund me. I bought this phone using an account of which I'm paying monthly but the phone is not with me.