Vodacom Oppo phone

On the 15th June 2021 at Voda4u store in Centurion Mall. I went there looking for a new phone, the sales assistant by the name of Mpho showed me an Oppo A74. I explained that im student and also run a business so i needed avery good phone. Thats when he insisted that it is a good phone. I then took a phone. I had a phone for about 2days it was overheating, rebooting it self and deleting very important files. I then call the store to complain. I was told by Mpho to give it s chance. Indeed i stayed with it for about 6 days and i took it to the shop, when i got there i was told to bring it on monday. Monday i went and spoke to the supposely an Oppo Manager by name of Nizza and explained what was happening with the phone. He was very rude. I then told them i needed other brand not Oppo. So they advise me to leave the phone and they will send it for proper check. I did left the phone on monday and receive a call on Thursday to fetch the phone. I went there and was told nothing is wrong with phone. I asked them to show me job card as aproof that it went for repairs or check-up.insisted that i dont want the same brand rather they give me other phone than oppo brand. They refused i since left the phone at store. Im very frustrated and angry because i use my phone for my school work as well as my business. Please assist urgently . Phumelelo no: ***