Once the giffgaff SIM is activated, you have two options to configure data roaming on your device:
a) You can use the automatic option by selecting the data connection that appears on your device when you insert the SIM.
b) You can also activate the connection manually. In order to do this:
Go to ‘Settings’ on your device and select the ‘Connections’ option.
In Connections, select the ‘Mobile Networks’ option then ‘Access Point Names’.
Click ‘Add’ and you will see blank spaces to fill with the following information, ensuring that the rest of the spaces stay blank. Name: giffgaff APN: giffgaff.com, Username: giffgaff, MCC: 234, MNC: 10
Finally, choose the NPA you just created by pressing the screen above. To use the giffgaff data network, simply disconnect from WIFI.