I lost my SIM. What should I do?
If you just lost your SIM you can activate any unactivated SIM and swap your number to it. You can use a SIM you have already or order a replacement SIM.
Make sure you log in to your giffgaff account when you activate the new SIM. If you don't, you'll create a new account with a new number.
If you lost your phone too you should report it lost so it can be blocked and no one else will be able to use it.