Use MTN as service provider at your own risk - you're most likely to lose everything

My phone was ****** and I'm trying to blacklist the number and phone with MTN so that I can do a swim swap. Its been 8 days and MTN is unable to do the blacklisting. The person who stole my phone has been able to unlock the phone and started making *****ulent transactions. I have contacted MTN contact center, visited various MTN stores, sent an email to the complaints department and they all cannot help me. All my accounts are linked to this MTN number and the person in possession of the phone and sim card is changing all my passwords. My regret is using MTN as a service provider and actually registering the cell phone number to all my accounts.