Bundle price is deducted from your top-up balance if you are on a top-up plan. If you run out of credit, the bundle will be paused and re-activated once you top up. You can view your paused bundles on MyGO and the GO app when you click on Manage Service.
If you try to buy a bundle, but you do not have sufficient credit, you will be notified during the buying process. You will get a prompt to top-up first. After your top up, you can subscribe to the bundle as required.