You need to contact customer services on 202 from your handset or 0344 809 0202 from any other phone, when asked about the purpose of your call, then say lost / stolen to get through to an agent.
You are only allowed one free number change, and you may be asked the reason for the request.
- Xperia 1V - o2 and Spusu - Pixel 8 Pro - o2 and Vodafone UK
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.
Currently using: Pixel 7a (O2 & Lyca), One Plus 6 (Sfr), iPhone 12 Pro Max (Vodafone)