Unjustified debit order from MTN

I had a contract with MTN which ended a few months ago but they still continue to debit my money. I called and even went to the stores to see if they can stop or explain why do they still debit even after my contract had elapsed. I’m sick and tired of being taken from pillar to post without proper course. I went again to the store not so long ago and the lady that was assisting told me that there’s no profile because all was cancelled and to date they still debit my money, this is really frustrating.