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 ]
Hope that this helps you.