VERY BAD CISTOMER SERVICE FROM MTN

I have been struggling for 4 months to return a phone to MTN. They picked up the phone on 27th of Sept 2022 and have since blocked my sim on a paid account to prevent me from using my data for which I pay every month. The phone that was returned will not be paid as I never used it but get faily threaths to pay for it. I am now thinling of cancelling both contracts with MTN due to their utmost poor and non existing customer care - jow do I pay a data only contract only to get blocked necause of a cancelled upgrade on another phone ?????