OOPO and MTN

So on the the 3rd of July I upgraded my contract with MTN and got the Renno 12 Pro 5G. This is a lovely device, but I can't receive incoming calls. Then it actually is not a pone. I am the only South African with a Cellphone that is not a Phone, but just a device for WhatsApp actually. So MTN does not help me with numerous calls and emails to the call centre and visiting the Branch at Mooirivier Mall Potchefstroom. It has been almost 3 weeks without incoming calls. I tried to give back the Phone as well as migrate back to my old contract, with just a You can't do it Tannie!!! this is all a joke. Imagine yourself going to the shop 4x, standing in the shop, as MTN does not allow sit down for an hour and a half with , they will phone you. HENCE MY PROBLEM, they can't phone me!!!! The lady that helped me with migrating was Jo-Ann, the Manager is Annelize. ***. But anyway they have no answers, don't want to swop my phone, don't want to change my contract and only put me through to customer care, who does not answer the phone, neither do anything about my problem. So now I am stuck with OPPO for 12 months and cannot recieve any calls, so no business for me to receive a salary to pay my aacoutn at MTN, but who cares there phones work!!!.