Customise how airtime can be replenished on your package. You can choose to block all usage that falls outside of your monthly Airtime amount or to automatically add Airtime in increments.
With in-bundle only selected, once your Airtime is finished, you will need to topup your airtime manually.
With this option, your package gets topped up with mini airtime bundles when you are at 90% usage until the specific maximum is reached. This allows you to have the control to avoid bill shock, but the flexibility to not get cut off when it matter most.