hands-free car cradle iPhone4S

[brownpods]

I have purchased a replacement cradle from Mercedes to replace the previous one which came with the car (used), as these are phone/model specific, so now have the specific cradle for my iPhone4S. The cradle just clicks into the top armrest compartment. Cant get it to work, its charging the phone but not connecting for calls and after trying for a few seconds the car screen goes to 'phone off'. (its not bluetooth of course,as its an older car). I recall from a previous car i had which also had a factory fitted cradle (different phone), that I had to go into the profile menu to change it to hands-free or headset mode to make it work with the integrated phone/radio system and the steering wheel controls. Wondering if its the same with the IPhone4 but I can't seem to navigate to where those profile options might be (usually show options like silent/meeting/vibrate/headset/hands-free etc). I know it has the little mute button on the side of the phone but that doesn't seem to work for this purpose.
Help !

 

[kch50428]

Perhaps a Mercedes dealer can be of assistance...