DISA to Trunk

[Tpanasonic]

Hi

I have NS1000, connected to Grandstream (Call Center) via SIP trunk.
i can make and transfer calls between two PBXs, with no problems.
what i want is to activate the DISA message so when the NS1000 receive a call and the DISA opens the client can reach the Grandstream by dialing 0, please advice.

 

[obtsystems]

If you set disa 501 with 0 dialling the Grandstream they can hear a message and dial 0 to call the Grandstream group