hi mohammad, welcome to gifgaff
You will first need to get your SIM activated(with a min £10 topup). When this is complete you will be able to view your randomly assigned number at http://giffgaff.com/dashboard
Once this is completed, you need to install some internet settings. Easiest way to do this is by sending a text with the message “SETTINGS” to 2020 Alternatively if this fails, you can input some settings manually
Go to Menu and then Settings > More Settings > Mobile network > Access Point Names. Press the Menu key(usually bottom left) then choose “+New APN”
You see a list, please fill them up as shown
Login - Username: giffgaff
MMS proxy: 220.127.116.11
MMS port: 8080
Now press the Menu button(usually bottom left) again and select Save.
Select the profile named giffgaff by clicking on the circle next to the profile named giffgaff until a dot appears..
Your phone is now configured for giffgaff's internet and MMS settings.
Please see: http://community.giffgaff.com/t5/giffgaff-Top-Tips/The-giffgaff-Internet-Settings-Guide-Setup/td-p/2... for more details
You'll need to add some settings (called an APN) manually for your phone to access the internet and send/receive MMS messages on giffgaff. Here's details of how to do that for android phones -
Android - http://goo.gl/iEsCXZ
You may need to turn your phone off and back on at this point.
If you're still having problems, there may be a problem with something other than your phone's settings. Firstly, check the obvious stuff. Make sure your phone is unlocked or locked to the O2 network or your giffgaff sim won't work. Check to see you have an active goodybag with available data or a PAYG credit balance on your 'My giffgaff' page (You'll need credit for MMS messages as they're not included in goodybags). Next, check if your phone has been switched to airplane/flight mode as this disables all connections, including mobile data. Lastly, check you have mobile data enabled.
If you're still having no luck, check for signal coverage and maintenance in your area using this site -
Finally, you can try what's called a manual roam. Check out this link for info and instructions -
PLEASE NOTE - Apparently the 2020 text settings are incorrect at present as is the giffgaff APN app, so I'd recommend not using those for now. Doing so can redirect you to the wrong site when you want to top up.
Hope that helps