Return policy and a defective product

Bashion here. I bought a Huawei y11 pro through contract at Mtn store mega city mmabatho. On Wednesday the 13th of March at 12:30pm I went to collect the device they opened it in my presence, when I got home I found out the Camara if faulty so on the following day at 11:00 the 14th of March I went back to the store to report that and ask for a return or the change of brand, the manager was insisting that the phone is fine I even took him a picture to show him and prove to him that there's something else wrong with the phone. They told me to wait for the Huawei technician to come and look at the device, on the 15th the technician came and took a look at the device and he confirmed that the Camara is indeed faulty,and the camera is wasn't even positioned to well, they mentioned it something to be like OB something, mind you all this was done within 48hours.So I wanted to change the brand to Samsung as I do not trust Huawei anymore, they are saying they can only exchange with the same device model or I pay R20000. Now I don't want the device I want to make a return and cancel the contract. The device is still with the Mtn store... I am so sick to my stomach, this is ******* at its best. The store says they do not have the returns policy how sick is that MTN south africa have the returns policy but the particular store does not have the returns policy this makes me sick. The Regional manager to this day insists I take the same product imagen. I don't want the new product I want to cancel the product or change the brand that's all