UNABLE TO BLOCK SIM

Trying to block my 13 year old's SIM as her phone got ****** and unable to do so at they do not want to assist me her parent and legal guardian. I am told she needs to phone in to answer security questions. She phones in and fails 2 questions as she doesn't know her ID number and the last two cell numbers she called out of her head. I phone again and speak to the supervisor Thabani and he insists that she needs to pass the questions. I say to him why doesn't he give me the last 2 numbers he called out of his head and see if he passes. He tells me it is irrelevant because so I say to him well if he can't remember the last two numbers he called how must a 13 year old remember? YOUR SERVICE AND PROCESSES ARE USELESS. Now a ***** is walking around with her cellphone and her SIM which is still unblocked.