If you gave them any codes or personal details, Change your O2 password too and any others that use the same details. Notify your bank if you haven't done so already.
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.
