To use Text Top Up you need to register for the service.
From within AIB Internet Banking select the 'mobile services' option on the left of the screen.
Click on the 'text services' option.
On this Screen you will need to:
When you have entered all the details click 'confirm'.
For security purposes you will be requested to enter one random digit of your PAC.
You are now registered for Text Top Up and can start topping up immediately.