Are you trying to make your first top-up?
Ways to top-up at giffgaff
online credit /debit card top-up
You can use a credit /debit card to top-up online or buy a goodybag. The minimum top-up is £10 and the maximum £30
You can buy a top-up voucher and use it online or by dialing 43430. Where to find a top-up voucher
Recurrence & Auto top-up
Set your goodybag to recur each month, so it automatically renews itself. The easiest way to top-up is to set up auto top-up. You'll be able to configure the amount you want to top-up and maximum amount of top-ups per month.