You can remove the content bar (which is set to ‘On’ by default) at https://www.giffgaff.com/profile/details#adultcontent using a driving licence or passport.
Due to a number of technical and security reasons, this is the only method of removing the block. The process typically takes no longer than 24 hours; you’ll receive a text when it has completed.
If you find that you have problems doing this, check https://community.giffgaff.com/d/3017767/1 for information on why the removal of the restriction typically fails, and if that doesn’t help you to resolve the issue, you could contact an Agent at https://support2.giffgaff.com/app/ask/Calls-texts-and-data/Controlling-Adult-Content/form/
Agent replies can take up to 24 hours, however, they’re usually much quicker than that. You’ll find any Agent replies at https://giffgaff.com/support/questions (you should also get an e-mail when a message is received there).
You can find full details on removing the block at: https://www.giffgaff.com/help/articles/how-do-i-turn-off-the-adult-content-block