If the goodybag has already gone "live", giffgaff are unable to do anything about it.
They have several times explained that the system does not allow any changes to be made to a goodybag once it has started. (A forum search will throw-up several similar explanations)
giffgaff always has the choice, of course, to make you an ex gratia payment, but I don't know why it would in this case. I wish you well with it, but the bottom line is that you should check such things before you commit to buying them.
Use the contact an agent link if you think it's necessary - but don't hold your breath waiting for their reply. From what other people are reporting, you'll be lucky to get any reply at all for days, much less one which actually addresses the question you raised !
Good luck !