MTN, where's my new phone????

Upgraded to iPhone 12 mid December 2020 being told my phone will be delivered within 7 work days. It is 13 January 2021 and nothing. The worst for me, because I don't mind waiting, is when I phone the retentions department, they put the phone down every time when they hear I talk about the iPhone 12. And even worse, I am already paying for the new contract, but don't have the phone. What must one do to get answers? Went to a branch, but they said they are a franchise and they can't help.