Hello all. I have installed an ntg 2.5 sat nav unit into my 2010 b class,The one with the sd slot and built in cd changer. What do I need to play my music from my phone? I have an aux port but can't control the music from the steering wheel if I use a Bluetooth adaptor on this. So many interfaces for sale I don't know what I need. Does anyone know how or have any suggestions. Cheers all.