Hi yes you can use sim swap.
Here is the method to perform a SIM Swap.:
1.Back-up all your contacts and texts saved on your SIM to your phone memory, as these data cannot be transfered through SIM Swap.
2.Log out of your giffgaff account, and click "Activate SIM" on the home page. Or click here-http://giffgaff.com/activate-sim
3.Enter the Activation code of the New SIM card.
4.When on the account registration page, instead of registering, log in with the link in the "already registered?" section.
This is where SIM Swap starts. It will confirm that you want to swap SIMs. (You need to double check the serial numbers, just in case.)
5. After choosing "Yes" each time you are asked, your old SIM will be deactivated, and you will lose signal.
6. Put the new SIM in your phone, and it takes around to 10 minutes for the SIM to become active.
The best thing is to leave the phone turned off with the new SIM in for 10 minutes, then turn it on and off until you get signal.
All Giffgaff sims are dual and hybrid sims that contain a micro sim which easily pops out.
Have a good day 🙂