Handset to be blacklisted/blocked

Good day, I have been trying to get a handset blacklisted/blocked and have been trying to do so for almost 3 weeks without any positive feedback. I was ****** at gunpoint from cellphone on the 30th March and have been trying to get the cellphone blocked in order to get an ITC number for a case number at the police station so that I can put in an insurance claim. I have also been to the Cell C shop thrice and still nothing have been sorted. This is a prepaid phone and I have been a loyal customer to Cell C network for a very long time as my son and husband uses this network. The call center customer service have been pathetic and I feel like I am the ********. I have the original box with both Imie numbers and still they say the can't help me. I can even get proof from Edgars where bought the phone in 2017. I am truly lost for words at this stage.