Just log into your My O2
http://www.o2.co.uk/myo2 and select the option to "bring in other products". Follow the instructions on the subsequent web pages.
I have no affiliation whatsoever with O2 or any subsidiary companies. Comments posted are entirely of my own opinion. This is not Customer Service so we are unable to help with account specific issues.
Please select the post that helped you best and mark as the solution. This helps other members in resolving their issues faster. Thank you.