MTN - contract change

MTN

I have been an MTN customer for over 15 years and always in a contract. I wanted to do an upgrade to the Apple IPhone 12 mini. I misunderstood the price difference between the monthly premium of the 128G phone and the 256G phone as being R600 more expensive. The store assistant reassured me that I would have enough space on the 128G phone to transfer all the data from my current iPhone (sitting at approximately 98G usage). I decided to go ahead with the contract for the 128G Apple iPhone mini. I took the phone home and attempted to transfer my data. This failed giving me an error that there was not enough space on the new device to transfer successfully. The new phone was subsequently found to be faulty by both Apple Store as well as MTN technicians and I was offered a new IPhone 12 mini 128G. In the interim I learned that the price difference between the 128G & 256G was in fact only in the region of R100 per month. I informed the store that I would like them to keep the new phone they are offering me and that I would like to amend my contract to the bigger more expensive contract for 256G iPhone 12 mini. I have not opened my new phone, have never even removed it from the store. They still have it. I would essentially just like to change my contract to the more expensive phone with more storage. I have waited 2 weeks for a response and today have been informed that my request has been declined. In the meantime I have been paying for my new contract for a month without having a new phone. My request is so simple. My request will make more money for MTN as it is a more expensive contract. They will not lose anything because my new phone is still in the store, and is in fact not my phone yet. I cannot understand why my request is being denied purely on the basis that I have signed a contract. For such a simple request to take 2 weeks to get a response without assisting me with my problem is unacceptable. With a bit of personal touch and applying some intellect and logic, there should be a simple solution. Please restore my faith in MTN. A brand I was once proud to be a part of.

Please help!