Upgrade Gone Wrong

Tried to upgrade existing contract via website. Gave errors. Phoned and did the upgrade via phone. When the new handset arrived we realised that it is 32GB and the old one was 128GB. We phone and asked if we can alter the upgrade to get bigger phone. Instructed that it is no problem the phone need to go to an MTN store. At the MTN Store we were informed it has to be a spesific MTN store. Went to big one in Menlynpark on 1 November 2019. Took more than an hour to book the phone in. We were instruted to call with the reference number once phone is booked in. We have done that on 1 November 2019. Promised between 7 and 10 wokring days the problem will be solved. Since we have now phones 5 times and explained the situation without any answers of feedback whatsoever. Its now 30 workings days later without any contact from MTN and if we phone after 30min on the phone the answer is always someone will call us back without any call back. Please help!!!!!!