Depends on if you are pay monthly or pay as you go @John15
Pay monthly - 202 or 0344 809 0202.
Pay as you go - 4445 or 0344 809 222.
If you have lost your sim, you need to report it as such - Guide: Lost or Stolen O2 Device? - How to Report it
Please note, this is not customer services and we cannot access your account. Do not publish personal details (email, phone number, bank account).
Link to our guide on how to contact them can be found here
