when try to do outbound call from .Net client an error appears"Disconnected[Remote disconnect/403:SIP-forbidden]" any idea about this error ???

This error is returned when the remote party for the SIP session rejects the call attempt in certain scenarios. In most cases, this would be a PSTN gateway or SBC of some sort - probably Cisco or AudioCodes. If Cisco, run debugs "debug ccsip messages" and "debug isdn q931" (if SIP trunk, just the first) to see why the gateway is rejecting the call. If AudioCodes, follow the support instructions to enable syslogging and take a look at the output.