Blacklisting of device

I've been an MTN customer since getting my first phone and have always trusted the company. In 2023, I took out a contract phone with MTN and insured the device separately.

Due to maternity leave, I fell behind on payments in 2024, and the account was eventually handed over. I have since made payments to the debt collectors.

My phone was ****** on Sunday. On Monday, I contacted MTN and was told my SIM had been blocked and that I needed to visit a branch to blacklist the handset. At the branch, I was informed that the SIM had not been blocked and that the phone could not be found on the system because the account had been handed over. I was then referred back to customer service.

Customer service also claims they cannot locate the IMEI or handset details. This makes no sense. MTN supp**** the phone on contract and can see the account was handed over, yet nobody can tell me who is responsible for blacklisting the device.

I need the blacklist/ITC confirmation for my insurance claim. If MTN cannot assist, I need a clear explanation of who is responsible and how I can have the ****** device blacklisted.