MTN incapable of providing an ITC number for a ****** phone

MTN can't pick up my cellphone on their system from the IMEI number, even though I have had a contract with them for years. Unfortunately this cellphone was ****** and I require an ITC number for insurance but they aren't able to give me one despite numerous calls to 135 and visits to one of the branches. What now MTN? I believe it's cell service providers that require the blacklisting of a ****** phone and yet it's your system that is preventing this from happening!