Bad Service

My iPhone 13 mini was taken in for repairs some time in September as it had power failure. I only got the phone back on the 21 Nov in a worse state than before . My phone was still under warranty as it was bought by my fiance in February, the shop then called my fiance to tell him that my phone needs R10 000 so that they can give me another new one in exchange for the mini as it cannot be fixed. Mind you we are still paying for the contract every month. Im angry and disappointed at the service