Samsung faulty device

I bought a phone, Samsung advised me that the A70 discontinued due to overheating freezing. This specific phone has bee replaced with A71, Telkom manager insist that they will fix and give me the old phone back. Samsung has agreed advised me that should rather give me a new phone the phone is under guarantee. The store manager was like over my dead body you will get your old phone back. The store manager an IDIOT no customer service orientated as well rude unprofessional. She told me you can lodged a complain nothing will happen.