Cellphone replacement

I bought a mobile device on the 10th December 2023 from Exact Mamelodi Denlyn and it was Vodacom locked. After 4 weeks the camera along with Google was not working and I handed it in on the 10th January 2024 for complain and they said they couldn't refund or exchange it instead they took it for repair for 2 weeks. After 2 weeks they called I went to collect but it was still the same and the manager said he doesn't have the authority to refund or exchange the device for me they have to get a go ahead from Vodacom. Kindly assist me with the situation as they promised to resolve the matter on Monday 29 but still I haven't heard from them