I have a 12 C class with the multi media and the IPhone adaptor cable option in the center console. When I plug the phone in it indicates it is charging so it seems the connection is good. I am looking for an AUX button or setting on the nav screen to toggle to the iPod section of the phone but no luck so far, can anyone help?

Should be able to play through Bluetooth.

What does the COMMAND manual say?

I'm not sure if it's the same as my 08 but the aux setting should be in the cd option. Push down to the sub menus and there should be an option to aux.

iPhone adapter cable option ?

You mean the USB port in the center console??
Not sure if this allow you to play from iPhone .

I have an USB stick in it, i play Music from the USB by putting the Disc button a couple of times to go to USB

I'm always plating over BT with my iPhone

Page 178, COMAND manual.
Select "Media Interface" from the list on Audio menu on COMAND.