Billing details

[JRT]

How to change my billing details?

[Enlli]

You can do it from My O2 and Manage your Account

[Cleoriff]

@JRT 

If using a PC, 

You need to go into MyO2  http://www.o2.co.uk/myo2

Along the top of the page you will see various headings. It's in the section BILLS AND CURRENT CHARGES. Drop down box will show "Change payment or address details" and payment details will allow you to change your bank details. O2 will send you a text to make sure it's you.