[AC Question]

So this is what I'm trying to accomplish. I have a Samsung tab and Samsung galaxy S7. I would like to use sidesync to link the cell and tab (tab being the hub) together and use it as a media hub while in my truck connect VIA Bluetooth. As it is right now I connect the tab and cell with sidesync and i can use media/GPS on tablet all being projected over in car audio but phone conversations are not. Am I missing something here ? I don't know what's going on, I assumed all audio would be sent to my truck as it already is when playing music.