Cancelation

I canceled my service with them on the 30th or 31st of December 2022 via an email because I couldn't get hold of the telephonically and they debited my account beginning of January 2023.i called them on the 4th of January and I was assured that was a last debit order from them, come month end January they debited my account again when I called them they said they only canceled lled my service on the 11th because they didn't see the email. How *********** of them and that cost me R500 my question to them was why should I be penalised for their administrative issues. They no longer reply to my emails