MTN WORST NIGHTMARE

I had a data contract which came to an end about 4 months ago. I went to their shop in Kolonade to cancell the contract. The lady "did" it on her computer but couldn't give me written proof. End of Oct I realised that they still deduct the contract amount from my bank. I went to the shop again on 5 Nov 2022. The woman cancelled it again. This proove that she didn't do it on my the previous visit. Now I received a statement again for the full amount and will be deducted from my bank at end of Dec. What must I do more. Can Hellopeter please help?