Bad service

I took a contract with Cell C four years back i kept on upgrading then 2020 i lost my job, they told me to send an email and also attach a proof that im no longer employed. I did send all those so by the time my contract was due for an upgrade i called customer service to explain that i wont be upgrading because im no longer working i would like to cancel my contract but however the agent told me that i can not cancel since its owing so now this year they are busy calling me to pay. I don't have a problem paying but the amount they are charging me is too much till to date they have not yet cancelled my contract and there is no data or minutes allocated yet i must pay. I spoke to the agent and the team leader but no one seems to be helping.