No Communication, huge bill.

The MTN website indicated that I could upgrade on 20 February 2021. Decided to use their online service, Mondo. After a few hiccups, received the new phone o 4th March. When I received my statement, I am billed over R1700 for a migration fee. My problem is that it was not communicated to me at all. Had I known that MTN apparently changed their early upgrade policy, I would have waited. Calling customer care, they sent me to Mondo. Mondo says normal upgrade sends me back to MTN. So now I am stuck in the middle with a huge bill. Receive evertime sms that says query has been closed.