Mtn - upgraded phone online, haven't received phone and can't cancel upgrade. More than a month.

Upgraded my contract online in Oct but did not receive my new phone. Been billed for a month. Are trying to cancel the contract and have spent over 7hours on the phone, over5 phone calls with online retentions and been escalated each time but they are unable to cancel my upgrade and just escalate the issue again. Still no help.