MTN Contract Double Deals

I am a MTN Customer now for almost 3year, I just upgraded my contract with MTN from Samsung A32 devices to Honor 90Lite double deal devices. The new upgrades i have with Mtn I received on the 01/03/2024 and i have been using the devices not even for a whole month when the device started to overheat. I went to my local MTN store in Vryburg to report the matter to them, they respond by saying they can do nothing for me, the only thing they can do is by sending it for repairs, which i declined because it doesn't make sense to sent new devices for repairs that you will be obligated to pay for the rest of the contract which is for 3years. I asked if they can give me new devices instead they said no. I also phoned head office explaining to them the scenario but they could not help they said because it was not a online deal, they advice me to go to my local store.

I took the devices in on the 28/03/2024 for it to be sent for warranty assessment, I then received a SMS back that states my devices was repaired and will be at my local store in 2 to 3 working days. I will not accept this devices because they are no longer new devices but repaired devices. MTN said they will blacklist my name if i refuse to pay them for rest of the contract. They want me to cancel the contract and pay off the devices which will cost me R16000. MTN refuse to help me please help.