Hi do this here, follow this to the letter..
iPhone Settings for a Better Browsing Experience
After itunes has updated your iPhone, it will reset your mobile data settings, so you will need to re install them manually. Or if you have access to WiFi go to the Apple App Store and download the "my giffgaff" app. https://itunes.apple.com/gb/app/my-giffgaff/id5712
Note picture messages cost 16p and are not included in any goodybags.
but are free to receive them.
The " Network " option has been replaced with " Mobile Data "
Check your settings against these.
There are four iPhones in the family that use these settings successfully. (3Gs, 4, 4s, 5) Running IOS 5.1.1 IOS 6.1 and ios 6.0.2
You need to install these manually...
Step 1: Firstly, check whether you have an old profile. Head to Settings > General > Profile. If you can't see "Profile" move on to step 2. If you can see an old giffgaff profile, tap it and press "Remove".
Step 2: Go back to Settings > General and press "Reset". Don't worry, this doesn't delete any of your personal belongings.
Step 3: Hit "Reset Network Settings" and follow through. Note that this will delete your WiFi passwords! You may need to enter your passcode, at which point your iPhone will reboot.
Step 4: Go back to Settings > General > "Mobile Data" or "Network" (depending on your iOS version).
Step 5: Tap "Mobile Data Network". Now under "Mobile Data" enter:
APN - giffgaff.com
Username - vertigo
Password - password (this should already be entered by default)
Leave Visual Voicemail as it is.
Step 6 (Almost there): Scroll down. Under MMS enter:
APN – giffgaff.com
Username – vertigo
Password – password (again, this is the default)
MMSC – http://mmsc.mediamessaging.co.uk:8002
MMS Max Message Size - 2097152
Once the settings are in, turn your iphone off ( via the red slider ) till the screen is completely blank. Then reboot. If you do not see the apple logo, the settings will not stick.