UNATHORISED UPGRADE

I RECEIVED AN SMS PAYMENT DUE REMINDER WITH A HIGHER AMOUNT THAN EXPECTED. UPON ENQUIRY, I WAS TOLD THAT I HAD REQUESTED AN UPGRADE VIA WHATSAPP. WHEN I TOLD THE AGENT THAT I ONLY CONTACTED THEM VIA WHATSAPP WHEN I GOT THE SMS WITH THE HIGHER PAYMENT DUE, I WAS ALSO TOLD THAT I USED AN 062 NUMBER TO MAKE AN UPGRADE. I TOLD THE AGENT THAT I DON'T EVEN HAVE AN 062 NUMBER, THEY THEN TOLD ME TO GO TO THEIR BRANCH TO CORRECT IT. i HAVE NOT BEEN ABLE TO GO TO THE BRANCH, SO SOME OF MY SERVICES HAVE BEEN SUSPENDED. I WAS NOT AWARE THAT I COULD REQUEST AN UPGRADE AND NOT ASKED TO PAY UPFRONT BECAUSE THAT'S HOW IT HAS BEEN DONE EVER SINCE I STARTED USING THE SERVICE.