@Garyl31
Try removing your SIM card and giving it a wipe with a dry cloth. If the issue persists, call into your local O2 shop for a free SIM swap.
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.