Shocking security questions - cannot safeguard your SIM after phone is ******

Shocking experience with customer care after my phone was ******. Called to block the SIM, and failed the MOST RIDICULOUS security questions twice. Questions for which the answers to are on the device that was ****** - what value did you last recharge with, who is your most called contact, things that busy people don't take note of! Absolutely appalled, after being a client for over 10 years... As a doctor, I sincerely hope that my SIM has not been accessed, after trying multiple times to block the SIM. As stated in the call, if there are any repercussions I will be taking it up with Cell C. More so, how am I to do a sim swap if I cannot get through the security check! Very disappointed, will not be rejoining CellC in future and will rather move to another service provider.