SIM900 ring sound

Hi,
When I use AT+Calm=0 I get a very shrill, unpleasant ringing sound when receiving a call. With AT+Calm=1 I get no ring sound.
The commands AT+CRSL=1, AT+CLVL=50......(all the audit commands) have no effect at all.
Can anyone help getting the audit commands to work?
Best regards
torben