Mtn is a ****

I had a contract with Mtn for 24 months data contract. In March this year I call the call centre to cancel the contract as it is ending in April indeed it was cancelled. I was confused last month May when they debited I reversed it. Now this month rather today I woke up and the debited double. Why are they doing this. I made it clear to the consultant that I am cancelling I don’t want anything to do with mtn.