Hi there and welcome to the community.
To set up your internet and mms "settings" using giffgaff,using your iphone.
If you have access to wifi,simply go to the app store, and download the "my giffgaff" app,or simply click onto the link below to go straight there and download the app.http://itunes.appld.com/gb/app/my/giffgaff/id571246020?mt=8
Once you have downloaded the app,open it and click onto MORE.
Then click onto Apn "settings" Your "settings" will now be installed for you.
If you would like to manually enter your "settings". Here they are.
1) check if you have an old profile.
2) Head to "settings"-General-profile. If you cant see an old profile,move onto number 2.If you Can see an old profile,tap it and press remove.
2) Go back to "settings"-General and press reset.
3) Press reset network "settings" and follow through.This will delete your wifi passwords,and you may need to enter your passcode,at which point your iphone will reboot.
4) Go back to "settings"-General- mobile data or network,depending on your ios version.
5) Tap mobile data network. Now under mobile data.enter. APN-giffgaff.com Username-vertigo Password-password
Leave visual voicemail as it is. 6) scroll down,under mms enter. APN-giffgaff.com Username-vertigo Password-password MMSC-http://mmscmediamessaging.co.uk:8002
MMS max message size-2097152
finally,give your iphone a few minutes to think and you should be up and running.
Also take a look a great guide,by clicking onto the link below.http://community.giffgaff.com/t5/settings-for-your-device/How-to-giffgaff-iphone-all-ios-versions/ta-p/3522027
If you have updated to iOS-7,check out the link below,cheers.http://community.giffgaff.com/t5/Settings-for-your-device/iOS-7-Internet-and-MMS-set-up/ta-p/9911035