No sorry, not possible.
To get an account in his name he will have to take a new one and pass credit and security checks etc.
Best done when the current contract ends so there are no additional charges and you can transfer the number to his new account too.
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.