Cell Con artist

I had a contract with cell c back in 2016 and the contract was due for an upgrade in July 2018.

They have been debiting my account continuously and continue to harass me that I need to make payment for a phone that has been paid off and I was not even sent an email for an upgrade. when I tell the m to cancel my account on the phone they inform me that I have an outstanding charge and everything was paid in full in August. They have been taking money from my account and this it ****ing unfair no upgrade was offered and they continue to blow my phone...