MTN ***********. Debited but don't have a contract

July 2022 to my surprise I was debited an amount on R450 by MTN. Ive never had any relationship with them. I disputed and stopped the debit order. August R988 debited again. I'm so furious because I even checked the credit bureau to check if there's someone who took a contract **********ly using my Identity and there is no such. My question is how does MTN validate bank accounts and how come they can debit a stranger's account without the mandate. Can they just cancel a stupid debit order.