Hello and welcome to the forums - thanks for joining!
By voice talk, do you mean use the phone as a telephone or do you mean use an app that requires a data connection?
If you mean use your phone to call people, then you would be charged as per your contract. If you mean using an app that requires a data connection, you would not be charged (or it wouldn't count towards your inclusive data bundle) for any app that uses a data connection if you were connected to WIFI... if you wanted to use an app that uses the data connection where there is no WIFI, then you would be charged (or it would count towards your inclusive data bundle).
Hope that helps... if I've missed your point completely, let us know and we will try to help you a bit more!