@alanahthompsonYou will need to Call Customer Services on 202 from your o2 phone or 0344 809 0202 from any other phone, as if it you do it in myo2 it will send a verification link to the old email address.
Current Phone: Sony XPeria Pro-I and Motorola Razr 5G
I also have a Planet Computers Gemini
I work in IT as an Enterprise Messaging and Collaboration Tools Administrator (Office 365, Slack and much much more) and manage hardware both Mobile and Desktop / laptop, my desk is a bit like PC World
--
We are all customers and dont have access to any o2 accounts