Ackermans Mthatha is a ****

Hi I have a problem with Ackermans, My sister bought an iPhone XR at 3028 Mthatha Circus Trian Shop 222 on 03 March 2025 and had to return the phone on 24 March 2025 because it had stopped working. We gave them the phone to fix and ever since we have been going to the store to check the progress but they are telling us they dont know where the phone is and they cant trace it which was alarming because we have the Return Request slip from them with the tracking number. Today we went back again and they requested us to deactivate the Find My iPhone which seemed very sketchy to use. Please help my cousin get her phone back