Just ran into a bug that will cause their customers some grief.
If you do a clean install of the OS of the phone that was registered as your authentication device and reinstall the app afterwards, ABSA's system thinks it is a new device, and the verification messages don't come through anymore.
If you then log into IB via a PC and try to do it via the website, it informs you that it requires a push message acknowledgement from the 'original' device before you can add a new one.
You can also not unlink the original device before adding a new one, because that completely messes up the works, and you won't be able to use any banking function again that requires verification unless you visit a branch to sort it out.
The same thing happens when you do a clean install of the OS on a device that was previously registered for online streaming services like Netflix, Showmax and DStv Now. They all think it is a different device and add it to your quota.