Should I advise my friend to beware?

A friend of mine just became reacquainted with an old friend through fb. They talk often, there are days he doesn't call and don't respond too quickly to text messages. For example: She texted him and he didn't respond until a couple of days later stating his phone was messed up. When he called, he called from another phone. That sounds really suspicious to me. He claims he works a lot too and that's why he isn't as available as much as he should be.