Sometimes phone usage requirements vary from month to month.
I have the £12 goodybag but am nearly up on my data allowance.
The £15 goodybag would have been a better choice for me this month.
When one of the allowances is up, why not have an option where you can give permission for giffgaff to upgrade you to the next goodybag up?
So when my internet runs out, giffgaff take £3 off via my direct debit, and I go up to the £15 goodybag and then start using the extra internet this permits me.
This could work in the same way for minutes and texts.