Mark got a new Android Phone with T-Mobile and wants to know if he can use Google Voice instead and avoid using his minutes. Leo says no. Google Voice would still use Mark's minutes. Voicemail uses only data, though. Options for data only usage include include Tango, Skype, and Talkatone.
There has been recent talk that Google Voice will soon be merged with Hangouts. This could even mean that Google Voice as we know it will go away.