Mercedes-Benz 2008 C-Class Operator's Manual page 233

Controls in detail
Audio system
i
If no SIM card is in the mobile phone, with a
few types of mobile phones NO SERVICE ap-
pears in the audio display. In that case, you only
can make an emergency call on the mobile
phone itself, without the use of the audio control
unit.
Placing a "911" emergency call with the
phone locked
i
If the mobile phone is locked, you only can
make an emergency call on the mobile phone it-
self, without the use of the audio control unit.
232
CDMA network phones
Placing a "911" emergency call using
audio control unit with the phone un-
locked
Press h button to switch to tele-
phone mode.
Enter 911 using the number keypad on
the audio control unit.
Press s button.
or
Press n for dialing to begin.
DIALING appears in the audio display
while the telephone establishes the
connection.
Wait until the emergency call center
answers, then describe the emergency.
Placing a "911" emergency call with the
phone locked
i
If the mobile phone is locked, you only can
make an emergency call on the mobile phone it-
self, without the use of the audio control unit.