@georgiana I think I would need more context to really make a suggestion. Like just a single word in the text thread isn't enough. If it turns out the girl was bullying him and he lashed out, I would opt to explain how he should have handled the situation (block her, not engage, etc). If it turns out he's harassing her and called her a B for not answering, much bigger consequences (take phone, huge discussion on consent and respect, etc). You probably have more details than were presented, but I certainly wouldn't pass judgment just based on one word.