Terrible service for elderly customer

I tried to assist my elderly father with a sim swop after his phone had been ******. We purchased a new SIM card and contacted the service center to assist with the process. I explained the situation to each agent and informed them that I was calling on my fathers behalf and and I would hand the phone to him if they needed him to verify his personal information such as ID number and address, this was fine until the security questions were asked. my father is hard of hearing and struggled to hear the the questions. He asked the agent if I could repeat the questions for him and relay the answers, however the agent insisted my father answer as he is the account holder, despite him telling her repeatedly that he was having difficulty in hearing. The first call ended in a failed security test and we were told to call 135 again and restart the process. She informed us that after three failed attempts the profile would be blocked but she could not tell us what to do if that happened or give any reason why we failed the test. The second attempt ended in another failed test, the agent said he was unaware of the three failed attempts leading to a blocked profile and told us we could call as many times as necessary, but we now had to recall 135 as he he could no longer assist us or give any information as why we failed the test again. The third attempt was also a failed test and the profile was blocked. the agent told us we would only be able to call 135 again the following day .we asked once again if he could give any reason or information as to why we kept failing the tests, he informed us that the codex system generated the questions based on the users profile and we must have answered a question incorrectly. A number of the questions were strange and irrelevant to my father. property values of addresses unknown to my father, the length of time spent in managerial posts he has never held, whether he still had accounts at stores he has never had. This has lead us to suspect my father may be a victim of identity theft. As a pensioner my father is unable to travel to a physical store as the nearest one is over an hour away. we are also unable to do the sim swop online using the self service pin as my father needs to call the service center to be validated through a similar security process to obtain the pin. A loyal customer for over 15 years, this has been an incredibly frustrating experience.