Sim card number deactivation

I am highly displeased with the service received from MTN. I have had my prepaid cell phone number with them since 2013/2014 after I got ******. I had to change my number because they had deactivated my number, even though I had called to block the number and wait for the police investigation before attempting a sim swop. Now they did the same thing again to me this year. My cell phone number that is attached to many different platforms and apps that I use with no notification. They then inform me I should have informed them that I won't be using my number, to whom do you advertise this information to before inconveniencing people's lives. Everything is attached to numbers these days. I tried switching over from a microSim to a nanosim in 2015 they told me they can't assist at the MTN store in Port Elizabeth Govan Mbeki Road near Traduna Mall. All new phones use nanoSims now. Yet they will just disconnect your number. It is unprofessional and rude to say the least. I asked the lady that I spoke to on Tues 23rd July to send me through to their feedback lines so that I can lodge a complaint. She instead dropped the phone. What type of service is that after a convenience to a customer caused by your lack of information.