MTN is completely ***********!!

I am seriously disappointed with MTN, i have been a customer for 15-20 years and this will definitely not continue when my contract expires. End of August 2019 i went to upgrade my existing contract and asked the weekend manager at the Kolonade mall outlet Pretoria, to show me the different colour options for the Hisense phone. After making my selection, they messed up and opened the wrong colour phone. I was told they can't change it now as the box is now open, they opened the box while i signed the contract, why should i pay for there incompetence?? I was promised on 3 occasions a black cover to hide the phone cover, and even MTN head office told me they will look into the problem, but its seems nobody gives a ****... well MTN i also don't give **** i will be leaving. I will definitely find a better deal at another company.. I am not using the phone, as it's not what i wanted, you guys are welcome to come fetch your mistake!!!