Incompetence, no response, Useless

I requested a cancellation figure for my 3 contracts and received the same on the 2nd November 2020, I made full payment of the amount. On the 4th on November 2 of my contracts were moved to prepaid as my request and I was advised to call in on the 19th of November to request closure of the 3rd contract. (All payments for settlement were paid). On the 19th I called in to cancel the 3rd contract and was advised that it is done. In December 2020, I called in to request my paid up letter and was advised that the 3rd contract is still current and that this will be escalated to a team leader. I was also advised to inform the consultant when I call in to refer to the notes on the system dated 19 November 2020. I called twice in December but nobody could assist and just advised that they will escalate and get back to me, nobody did. In January I called again and was advised that the cancelation did not happen, very furiously i requested to speak to a manager and after 40 minutes on the call the call ended. My statements show that after settlement in November I was billed every month for all three contracts from November, December and January, how is that possible? The billing of all three contracts used up the credit in the account for settlement of the 3rd contract. Now Cell C has the audacity to debit my bank account with what they deem owing to them due to their negligence and fault. I have an email trail that was sent to me that shows the conversation between Cell C employees where they admit that their system made an error and that their colleagues did not put through the cancellation correctly, so in this email they admit their errors and blame their system but they are not fixing their error, they just keep debiting my bank account without my consent. I want this resolved and i want my money back Cell C, I need my paid up letter.