Need ITC number

I had my phone ****** in a house break in recently and needed to get my phone blocked. I have ported my number to CELL C, but the MTN Sim card and phone are the ones that belong to MTN. I need to block my phone, but MTN has NO IDEA how to do this. I have escalated this issue and the store send me to the customer service and customer service send me to the store and store makes you fill out a form which is just another delay tyactic. I cannot understand how recalling an old account even though i have ported is difficult. Cell c cannot help me as the MTN Sim and phone that was ****** cannot be recalled as they never had any activity from it. All i need is for the old phone to be blocked which had an active MTN sim card in it. Its been over two months now with no luck and it is clearly incompetency for your staff members to be sending clients from pillar to post. This was escalated and communicated via email to no avail. All i need to simply do is block my old sim card and phone. How hard can that be for such a big telecommunications company such as yours?