Charging client when client blacklisted the phone

My phone was ****** the 09 May 2020. I have black listed my phone with MTN. In the time from then to 13 May 2020, all my airtime, Data and they baught more airtime on credit which i am liable for now from MTN. I have phone 135 they stated that i needed to do a simswop before that sim can be deactivated. Which is bunch of ******* as i could not do a simswop because i dont know some answers. By the time im trying to sort this out they cannot switch of my sim off like other service provider does. Soft lock.

MTN is ******* and i will not recommend them to anyone. There client service is bad and they do not know there process.

Worst experience ever. This is not treating customers fairly at all.