Worst service I have ever received

After requesting a settlement letter almost 18 months ago,settling my account and sending the proof of payment,settlement letter cancelation letter and copy of my ID to vodacom they have failed me dismally. I called a few months after this process to confirm all was in order and I was reassured by a "team leader" that they have recieved all the necessary documents and will process my request.

I assumed that I'd seen the last of it. Only to be surprised a year and a half later with them debiting my account. Suddenly I'm in Areears and my squeaky clean credit score is ruined. Somebody in Vodacom failed to act on my instruction to cancel the thousands that I paid was used to "prepay" my contract hence no more debit orders. After receiving no joy iv started paying again. The contract officially ended in Nov 2019. Iv tried canceling again today only to be told I'm in arrears how is this possible. Will this contract ever end. Nobody is willing to admit their error and assist.