What do you mean by calling a boy many times and not answering, or sending him a message and not returning?

If a boy doesn't answer your phone many times when you call him, and then he just doesn't return your message when you send him a message, then I think his meaning is already obvious, and he just doesn't want to talk to you. Don't want to talk to you, that's why he chose not to return your message or answer your phone. Maybe there is any contradiction between you that led to him, or maybe there is no contradiction between you, and he suddenly has it. Then it is very likely that he may have found someone else he likes, and he will choose to completely sever the relationship with you in this way.