Adding another 02account to my o2 account?? No idea

[Maggoo76]

Samsung s8 edge

[pgn]

It can be done, but it is a one-way journey that can be difficult to undo, @Maggoo76.
On the MyO2 page for "My O2 Products and Services" there is an option to Bring in or Add products, that's where you start:

[Bambino]

@Maggoo76 You can go to your My O2 page to the section 'Bring in products' http://www.o2.co.uk/myo2

As @pgn says, it can't be undone, so be sure that's what you want to do.