Poor service and unhappy customer.

Good afternoon. I cancelled my contract in Humansdorp MTN on the 3rd August 2022 because I started working overseas. I have the proof of cancellation and the pop for the cancellation fees.Now when I came back to South Africa I saw that mtn has been billing me different amounts every month. They have taken so much money from me and I am trying to get a refund but the service is so poorly , I keep on phoning 135 and they keep on cutting me off. They told me (135)that my contract will be cancelled on the 21st of August this year now but I asked for proof and they didn't send me anything. I am scared they will still take my money and I want myr refund of all the debit orders they took from me.Last month they took R808 and that is not even the amount my contract was per month. I am really upset with MTN services. We pay a lot of money to cancel and then they still take money from us. Please could someone assist me??? I am leaving to overseas again soon and I want to sort it out before I go.