No helplines as giffgaff is 100% online.
Most phone manufacturers now include giffgaff's APN settings in their software updates, for most of their newer phones.
This means that simply putting a giffgaff SIM card into a phone with the settings will automatically set up the internet and choose giffgaff as the carrier.
Often a simple phone restart will fix things.
If this doesn't work, then you will need to manually install the settings
It's not a difficult task and to manually set up these are the settings required for your phone
password: [Leave blank]
Proxy: [Leave blank]
APN - Access Point Name: giffgaff.com
Password: [ leave blank ]
MMS proxy: 18.104.22.168
MMS port: 8080
APN type: mms
Do NOT press the " Reset Settings " button when you’ve done this. Just restart your phone.
Depending on your phone, you may also need to add the following if asked for it:
Authentication type = PAP
APN type = default,supl,mms
APN protocol = IPv4
Bearer = Unspecified
If you have an iPhone running iOS 7.1.1 or later then by far the easiest way to get the giffgaff settings is to download and use the Apple approved carrier profile from this link
Hope that this helps you.