We have recently installed a new DECT system and created the extensions on CM as basic SIP as they are single line handsets. The calls work fine from and to all handsets. We have an issue though with supplementary services. To call forward a SIP freeset you enter *21*$# and this should forward the handset, but when you call the handset you just get cisco message "unable to contact dialled number consult directory etc"
Put a sniffer trace on and you can see the messages going to call manager for a 302 temporary move and Call manager ACK response acknowledging the call forward. Yet when you dial the handset and expect call to forward the sniffer shows CM then responds with a 503 service unavailable message and thats why you get the recorded message.
I have raised a call with the ASCOM people but they are insisting its a call manager problem as they send the "302 temporary move" SIP message but CM is not doing the necessary.