It is obvious to me that you are having difficulty understanding how to manage your gift gaff account if you want to end a regular payment being taken from your bank log into your account dashboard and turn off recurring goody bag and auto top up once done no more payments will be taken. If you then go into your profile by using this link
TO ACCESS "MY PROFILE"
You can remove your payment details. If you need any more help just ask
Are you OK now with your wanting to close down your giffgaff sim service or do you still need help.
Are you having difficulty navigating your online account and thus unable to make the changes we have advised. If this is so please don't hesitate to ask for more help, the guy's on this forum are the best in the business and have no axe to grind, they just love to help, also giffgaff like happy customers whether they be joining or leaving, so please don't hold back just chuck it at us and we'll give it our best bat.