Have a look at this post - if you're new to giffgaff there is most likely a bar on using the internet on the SIM at present.
Try doing a search in the community for San Francisco. It comes up with lots of tips for configuring APN settings. I've got an unlocked SF myself and soon got mine working on the internet. Unless of course your sim is still blocked to the internet.
I've had a check and can see that there's no internet bar on your sim, so if you're still having issues you'll have to alter the settings.
John @ The giffgaff Team
I'm having the same problems with getting online. My sim is activatd, and a £30 goody bag paid for. And I've manually put the settings in yet can't get online!?
Stewiek - have you checked with an agent that the internet bar has been lifted?
If it has - you're ready and should be able to use the settings in this post