Boyfriend issues?

So I just started dating this guy about 2 months ago or so. Yesterday I woke up to this random girl texting him early in the morning. No I didn’t check his phone. Anyways he said this girl called him and didn’t know who she was. He then started talking to her and shit on fb messenger. I didn’t read their conversation. I also haven’t dated anyone for a while so idk I don’t think this is normal bc I never would do something like this. It makes me think he’s interested bc if not why else would he do this? Idk I’m looking for advice here

Update: well we talked about it again and he then told me one of his friends used to date her. So there’s more to the story then what I know. There could be more idk. Point is, if it’s really the wrong number idk why continue it to fb bc that’s where they can see more pictures and everything about a person? Or maybe he don’t want her number showing up on his bill. Who knows.