Bad Online Service

Dear MTN, I cancelled my online contract with you, within the 7 day cancellation period, on 4 February 2022. I returned your sim card to the Rivonia MTN store on 5 February 2022. It was confirmed by Mondo on 8 February 2022 that my contract was cancelled. On 28 February 2022 you deducted money from my account via debit order. I have sent emails which you do not respond to. When I phone the customer care line, the consultant states that I need to phone 136. I am not sure how to phone 136, as I returned your MTN sim card. I am so disappointed with your online, email and call center service. I do not recommend MTN to anyone.