No one here will be able to solve this @AntonyGG as we are all customers like you.
Customer services will need to either create a new login for you, or de-register the number so you can take ownership.
All ways to contact them are in the guide below:
Guide: How to find help & contact O2
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 Do not publish personal details (email, phone number, bank account).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
