Unauthorized upgrade

I am writing with a heavy heart after I called your customer care line to cancel my *** number after my contract had ended, on the 26/08/2022 during the conversation with the agent we got disconnected, but as I was trying to call back I receive a text that my order has created reference number ***, when I call back I speak to another agent and he is telling me that I have upgraded but I have not chosen any plan, I want this investigated and I want my contract canceled I have suffered enough already today for 1200 more debit than I am used to

Regards Buntu Ngaphu