Dtmf signal issue with Cisco 7960

Hi all,

system info
Currently we are using Cisco IP phones with a SIP image connected to our Trixbox (v1.2.3 with FreePBX v2.2.1) server. To call outside we use a trunk between Cisco Callmanager (v4.1) and our Trixbox server.

issue
Not able to call in to a conference call and use our password number. For
some reason, the phone still registers “doubleâ€