If you have less than 5 minutes or 5MB left on your current goodybag, it is possible to activate your queued goodybag straightaway rather than having to wait for your current goodybag to expire.
Go to "My giffgaff", a new message will be available under your queued goodybag, click on this message to start the queued goodybag right now. The same operation is also available from the goodybag page.
The queued goodybag will immediately replace your live goodybag.
Please note that starting your queued goodybag early will remove any remaining allowance (data, texts, minutes) that you may have left on your active goodybag. See HERE