Headset Blacklisting

My 11year old son's phone was ****** and we tried to block it but couldn't. They asked him all sorts of security questions which he couldn't answer cause he can't remember all of them and they said they can't help. Is it so difficult to blacklist? It's not like we want to commit ***** just to get it blocked for insurance purposes and to get it replaced asap coz he uses that phone to communicate with me when I'm at work so that I can know that he's fine and not to stress. But at this stage I am terrified if something happens and he can't contact me. His life could be in danger and won't have any means to contact for help because the insurance won't help without the case nr. If something happens to my child I will hold Cell C responsible for wanting to know every detail from a 11year old who is just a child. I hope I will get a response soon so that I can still go and open my case and claim from insurance on Monday.