I buy top up vouchers and convert some of the amount as goody bags and leave some as credit.
Buying vouchers and converting them to credit or goody bags suits me. It keeps me in control of my finances in a way that I like.
I change the amount of the goody bag that I use depending upon my anticipated usage for next month.
My "balance" is the unused credit. Are you saying that users like me are to lose our remaining credit? Or should users like me leave Giffgaff?
However, I am happy to think that I may have the wrong end of the stick from your post and we need to change the wording or jargon to a fresher, more modern terminology, as long as any change is an accessible improvement on the current description!