If you mean transfer your number over to giffgaff then yes,
You would need to request for a PAC code from three,
Once you received your PAC code did you follow this procedure?
1.Log into your giffgaff account 2.Check your SIM is active 3.Go to "Help"> "Transfer your number" to load the transfer form 4.Fill the form, including the number you wish to transfer, the PAC code and the date you wish the transfer to take place on. NB this date must be within the next 14 days. 5.Verify these data to avoid any delay 6.Click on "Transfer your number to giffgaff"
If you request to transfer your number before 3pm, your number may be transferred on the next day. Requests made on Friday are processed on Monday. Requests made on Saturday and Sunday are processed on Tuesday.
This is what happens on the day you transfer you'll experience a loss of service at some stage between the hours of approximately 9am and 6pm - typically this is no more than a few hours but can take up to a day, so please make plans so you're not caught short.
On the morning of the day the port is intended to take place, turn your phone off and put your giffgaff sim into it. Then a few hours later turn the phone back on
If the porting is complete, your phone will say giffgaff on the screen
If not, it means the porting has not yet been completed, in which case just turn the phone back off and try again later
Remember, it does take a few hours to transfer your number, however - if your number still hasn't transferred after 6pm of the transfer day , please submit a private query to a Member Service Agent: Ask a giffgaff Agent, to help things get resolved ASAP, please include the following information
It is possible. First call three customer service (i think it is 444) and get your PAC code to transfer number to giffgaff. Then get a giffgaff sim and after activating your giffgaff sim you can submit the online form with the PAC code to transfer the number from three. It might take few days to transfer over. And you need an unlock phone as well or an O2 branded phone to work with giffgaff.