But she didn’t have any clothes on; she fumbled with a towel as she was apologizing for calling the wrong number. And if it’s videophone sex why wouldn’t the particpants undress? 
They (or at least the male) would be masturbating anyway.
No, it’s videosex, with clothes on and no masturbation.
Do you think they masturbate? I don’t.
They wouldn’t undress because that’s not how they have sex. They have sex clothed and with a headset on. She had no reason to call while naked. The meta reason of getting boobs into the movie is fine, but there’s no reason within the universe.