Voiceover question while on a call

Hi All, I had to get a replacement iPhone 4S yesterday because the volume button broke on the previous one. With this new one, I've noticed That when on a call, and I get an email of some sort, voice over does not say notification from email as before. Voiceover speech is turned on, when this happens. Any thoughts as to why this now occurs? Also, is your volume both on the phone and speaker phone supposed to turn down all the way while talking, or just down to a certain amount? Thanks for any and all feedback. Shane.