Thanks for getting back to me with a reply. Actually I have a small balance in my account, and I'm guessing here, aren't there others who do the same at most times too? Just to use a figure, not my actual balance that you can probably see, being a giffgaff staff member. Let's say my balance is 20 Pounds Sterling, and I knew I'd be getting additional pounds in June, during the next PB. I could currently donate 10 Pounds (or more if I wanted to) to giffgaff's fine charity ideas, without waiting for a later time, and having no choice of giffgaff's charity showing in the usual choices at that time, in addition to my choice of using only A PORTION of my credit, but not all of it, for the donation.
Yes, without really knowing, I'd be surprised how few members keep little, if any, credit in their accounts, just in case it may be needed, such as for long distance calls not covered by their Goodybags.
Edit. Just to prove a point for you, or me, how about a small POLL in here, asking without giving exact numbers or names, which giffgaff members usually have a credit balance in their accounts of AT LEAST 10 GB Pounds Sterling. No other info needed, just a YES or NO vote, for anyone with at least 10 Pounds usually left as a credit in their account.