Contract expired and they are still debiting from my account

I had a 24 months contract with MTN,though i was not happy with service i had to continue and just wait for my contract to come to an end,it was ending 15th August 2024,i went to the store to cancel,i was advice to come monthend as i already received my data for the month and the lady adviced me so i wont forfeit my data,ohk around 28th i went and i canceled successfully,i confirmed if it was canceled and i won't be paying following month,she said yes,15th September debit order went through,i rejected it,now again 15th October they debited again,im so furious,as i don't want to spoil my credit record with reversing debit orders,i went to the store Kroonstad branch the lady denies everything and she said its her word against mine,bad service ever as usual

Joyce Sinxesi