You went through your boyfriends phone and he had a missed call and a voice mail from another girl Should you be worried?
Well not unless you've seen him with this girl. maybe a question about homework or sports or something. if you really want you can listen to the voicemail but he may get upset over invasion of privacy. then maybe you can bring him up in convos of the girl if you are really worried but until then just keep it in mind but dont dwell on it.