Technical issues with 135 number and answering security questions.

My son was attacked and his phone was ******. We tried unsuccessfully to block his phone but as he was in shock, he could not remember details pertaining to the calls he had made and data bundles he had purchased. We tried to ring back to try the security questions again and from 6pm, option 9 on the menu to speak to an agent went back to the start of the menu and we could not get through. We still cannot blacklist the phone.