You must have less than 50mins of calls, or less than 50mb of data on your existing goodybag - in order to start a queued goodybag
"On your dashboard https://giffgaff.com/dashboard under your goodybag details you should see an option to start your 4G queued goodybag early. Just click and confirm you want to get rid of the active goodybag and the process will be set in motion."
See cancelling a goodybag or top up purchase
starting a new gooodybag early:
Log in to My giffgaff.
If you have less than 50 minutes or 50MB left in your goodybag then a message will appear under My goodybags.