MTN will fail to retain 22 year client

I am going to leave MTN due to their inability to manage insurance companies they use. I have had my iPhone 7 Plus for about a year. Before this I had the iPhone 6s Plus. I was ****** and iPhone 7 ******. I then submitted a simple insurance claim and after going through the painful process they said that although they have my phone registered as an iPhone 7 Plus, they have the imei number of my iPhone 6s Plus and won’t replace my phone. I have even been paying about R150 for the new phone where the old phone was only R100 per month. Basically I am paying insurance for nothing because of negledgence on the insurance’s side. What can Mtn do about this? At a bare minimum MTN needs to quit false advertising, but over and above that someone will replace my phone I was paying insurance for. If nothing is done this matter will be taken further. This contract was instated in 1997. I’m sure the newspapers too would want to hear of the experience of one of MTN’s oldest clients.