But on my bluetooth, you can actually turn the volume up on the phone and it increases the output volume over bluetooth. Weird...but it works on all the Galaxy phones i've ever had. Also...if you have Aux input and a Samsung phone, then get a Bluetooth receiver dongle that is AptX certified... your bluetooth will sound MUCH better via the AptX processing.
Also...save for offline listening works on most streaming apps. Try that to save your data.