Irritated by MTN who has been my service provider for years.

In May someone called me from MTN asking me if they could upgrade my package that I was on, saying I would get data etc etc. I asked how much it would cost and the guys said nothing. He eventually admitted there would be a small fee. I declined politely and put the phone down. Since then I have not been able to buy data from banking app. It keeps giving me an error. Someone told me at customer service, I was blocked and they needed to unblock me and I needed to switch my phone of for 20mins. I did that and still nothing. The next person I spoke to said I need to wait 24 hours for the block to be lifted. We are in October, still nothing. I spoke to numerous people and eventually was told that my pricing plan was changed. I never requested or agreed to this changing.. MTN customer service said Sales needs to assist me, Sales said Credit needs to assist. The number for Credit is never answered. Someone told me I just need to buy airtime and convert it into data, while this does help, it's inconvenient to have to try and remember USSD codes for everything. Just fix this MTN!!!