Sim Swop not banking details exchange

What an experience I just had. I am quite frustrated now.

I have been trying to do a sim swop since yesterday as my new phone requires a nano sim.

The agents keep on telling me that I can't because their system is declining me as the answers are incorrect.

I am reading from the call log who I called last and what amount of data I have left etc.

How stupid can their system be. I will rather change my network then to waste my time.