It sounds like your Bluetooth is working like mine. Music plays through the front speakers and volume is controlled either through the phone volume control or by pushing and holding the up or down arrows on the dash control (which controls the volume through the phone). Double pressing the up or down arrows changes the track playing.
I have not found a way to access the dash Bluetooth through the radio controls.
In with my manuals was a small (3*5) Bluetooth manual. Maybe you have one hidden in the glove box.
View my fuel log 2014 Mirage DE 1.2 automatic: 48.1 mpg (US) ... 20.5 km/L ... 4.9 L/100 km ... 57.8 mpg (Imp)