As we all know giffgaff do not and wont be operating a call centre so heres my idea.
With the other providers theres a Customer Care number, 150, 789, 450, 2020 etc that gives you a few hundred options by pressing numbers and playing messages then eventually if you still need to be given the option to speak to a Customer Service Agent.
If giffgaff were to create rather than a Customer care line but a Advice Line on lets say 43431.
It could include a large selection of help matters similar to the request PAC code feature via 43430 but on a much larger scale with advice on all the major features of giffgaff so callers are able to hear the advice on the above Help pages rather than be forced to come to the website for the information.
Example, customer calls 43431 and heard something like.
Welcome to the giffgaff advice line,
For advice on transferring your current number into giffgaff press 1
To learn about top up options and goodybags press 2
If your internet is not working and you need to request your settings press 3
Kudos this idea if you like it and giffgaff may look at it.