MTN CONTRACT

I have a problem with MTN i took 24 months contract it was suppose to end January 2021 and i was paying R178 a month for 2Gg data and 108 airtime and Xiami phone. A month before that was november 2020 i sent them emails that i wont be continuing with their contrants and im not upgrading after the expiry date they must cancel . They did not cancel it i have been calling them non stop they are not picking up calls you hold the whole day. Im reciving emails from them that im owing them 3 months payment and i dont even know for what im not even using the sim cards i destroy them after my contract ended because i did not even want a situation where by they will say im using their airtime and data. I have proof that i sent cancellation email before even the contract end if why they are not ending it i dont know i need help in cancelling this contract im tired of them trying to ***** money i dont have from me