MTN Business - Pathetic Service!!!!

I purchased an Iphone 15 (business account) in April 2024. The devices battery has been giving me endless issues where it heats up, runs down super fast and it doesnt charge. I have been contacting MTN and going into store physically since September 2024 and they have been sending me back and forth. They first told me they cannot book the phone, then they advised I have to come back and I have been running up and down trying to sort this phone out with MTN. A guy by the name Tamsanqa then advised me I should take the phone in directly to i Store, i then sent him the correspondence where I was liable to pay R300 in order for iStore to assist which I was not going to pay. He hasnt responded to me and has been ignoring my texts and calls ever since. I called this morning to ask MTN if I cannot return the phone instead and downgrade for upgrade for a better phone. The lady once again told me I need to go in store and they will assist me. I have been to multiple MTN stores and not one was able to assist me. I urgently require assistance regarding this. Pathetic Business service!