MTN are ****s and ******* with zero integrity!

I upgraded my contract over the phone, I have not signed any agreement with MTN to upgrade so the only agreement was via a phone call. I have a copy of the transcript sent to me from MTN outlining the cancelation terms. However, now that I want to cancel they refuse to honour those terms. They keep telling me there will be penalties for early cancelation beyond what was agreed I am happy to resovle and pay what was agreed but they refuse to help. It would also be a massive inconvenience to me to not be able to keep my number - They are holding me ransom and refuse to budge on terms they had agreed to. Despicable company with zero integrity.