Updating banking details problems

I tried to use the online chat service to update my banking details twice. The conversations were extremely unprofessional. I pointed out that the chats are not secure and I prefer not to provide too much details via the channel and asked that they updated my banking details. They answered that they first needed to verify that I am me. I informed them that there is NO way they can do that via the chat functionallity as it is impossible to know that they are actually speaking to the account holder over an unsecure line.( I have screenshots of the conversations and the unsecure indicator) They insisted that I then have to phone. I informed them I am not going to incur charges as I am contacting them. Please note: NEXT TIME someone offers to pay my bills let them! The two agents are Mandisa and Nozipho who were extremely unprofessional.