Why is it that sometimes I can adjust the volume using my steering wheel controls and sometimes I can't??

Also sometimes it just won't hang-up a call when I'm done! I keep trying to end the call using the 'speak' button on the steering wheel ...but it will not end the call unless I end the call physically from the cell phone itself!

This also happens when I get a busy signal when calling someone. It just will not hang-up the call until I hear the busy signal forever and finally disconnects!

I know it's not the cell phone 'cos it works fine without BT.