I've never understood why no-one blocks numbers in mangas. I'm almost certain she's not going to block the number but instead save it and create unnecessary drama in the future. I mean, I would at that point say no, hang up, block the number and tell the sister to inform the idiotic brother to never contact me again. If someone wanted my contact info, they'd have to ask me, if they don't want to be blocked. And no, that is not an overreaction. That's barely enough of a reaction.