You may find that you have accidentally added airtime credit and / or a queued goodtbag to your account.
Check your dashboard here https://giffgaff.com/dashboard
to see if you have an active goodybag on your account and/or airtime credit. Also You can check your payment history here https://giffgaff.com/account
Remember that you can use airtime credit to purchase another goodybag next month.
This may help to explain the payments. If not, and you still would like a refund then you will need to contact an agent. They may be able to help you.http://giffgaff.com/support/ask
Answers can be found here https://giffgaff.com/support/questions