Standard Bank don't want to change my telephone number

Last week I got an email from Standard Bank telling me about the new debit order verification system. Apparently I have to authorise new debit orders via their ATM or their banking app. Which I feel is a good thing.

So, I install their app, but it refuses to work because I am currently in Thailand and use a Thai sim and telephone number. I then sent an email to their help desk (as on their website) to CHANGE MY TELEPHONE NUMBER, because they have removed the secure message feature from their website.

Just to get a reply 5 days later to call them. Are they insane? Do you have any idea what an international call for an hour or three will cost me while they keep me on hold, or try to figure out how to how/who can do it?

I am really unhappy with them, because my life insurance will now not go through at the end of the month. Thanks Standard Bank for not changing my telephone number.