If your SIM card has been locked, you will need a PUK code. You can find this on the My Account portal.
For more information on PUK codes, click here.
Click the Asset Management menu option and then Mobile Management. The page displays all your live mobile services. Find the mobile number you need a PUK code for and tick the box to select it.
Select the Unlock SIM action from Select Actions then click Apply.
The PUK code will be displayed on the screen.
