Ackermans Capital centre in PMB refuses returns/refunds

Hi, my mom bought a phone on the 22nd of November 2024, it had problems cutting calls, and was very slow. It also had a problem everytime she's using internet. She went back to this shop on 25th to ask for exchange or refund, they completely denied saying the phone is okay now. But problem didn't stop she went back on the 29th, we argued for more than an hour they didn't want to replace the phone. Instead they said they will send it back to suppliers. Now mom have to wait 21 days without phone.please help. In Pietermaritzburg Capital center