Lack of Opportunities to block sim card

I'm on contract and my phone was ****** and I have been trying to get hold of Telkom customer care to block my sim. I have attempted 24times from 08:30am to 01:00pm (06/04/2018) and there has been no answer. My sim card is out there for the people who stole my phone to use, while i could possibly be accumulating charges from the calls and data used during this time. I am really disappointed