How can I remove a secondary line on my iPhone 14 Pro Max?

Hello!

I was trying to find the roaming toggle on iPhone 14 Pro Max with a tree uk sim (not esim), but couldn't find it in settings where it normally are located! ... so I thought , maybe try my moms sim, it didn't help and now I can't get rid off her number in secondary line, when trying to delete it a popup show with something about contacts, which I suppose will messup my contacts with her contacts!? And here Im ! ... I did manage to relocate the roaming setting, with a network reset! but the secondary line is messing up my experience with the iPhone! please tell my I can get rid off my moms number !? ... nothing on internet about this!

thanks in advance/ tomazo.

[Re-Titled by Moderator]