This is the process to sim swap here
http://swapmysim.o2.co.uk/Once it has started you need to keep restarting your new phone every half hour to force the change through.
It can take up to 24 hours to complete though fully.
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.