I think they are having you on
but if they are serious, it will be somthing account side so you'll need to call customer services.
Not sure if it helps, but I found this on their website:
First check in Online Banking that your alerts are set up to go to the correct number. If this is correct then please call our helpdesk on 0800 917 9170. Lines open 7am to 9pm Monday to Saturday and 8am to 9pm Sundays.
View call charges
If you would like to change your registered mobile number or email address, you can do so by:
using Online Banking, go to the ‘Alerts’ button on the left hand menu
visiting your local branch
calling us on 0800 9 123 123 (lines open 7am to 9pm Monday to Saturday and 8am to 9pm Sundays)
Don't forget, if you're updating your mobile number for Account Alerts, you’ll also need to register your new number in case we need to send you a One Time Passcode for an Online Banking transaction.
Go to the 'My Details and Settings' tab
Go to the 'Change OTP service phone number' link
You will be asked to confirm any changes you make
I think it might be "encrypted" text messaging that we need here, not "cryptic" though?
Thanks everyone for the troubleshooting here for @Amy3.
It's a bit difficult to say without more information, but having checked in general on our end, it could be the banking app may need certain protocols that only a specific app from the bank could provide. Another thing that came to mind is on a Samsung phone where you can block sending chargeable texts that may in some cases interfere.
You mentioned you were still waiting for clarifications from your bank @Amy3. I'll drop you a PM here on the forum shortly as we'd like to help in the meantime just to check over your account to see if anything can be identified on our end more specifically.