With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
cvCallGroupRev4
Cisco Voice Call Group Rev4
1.3.6.1.4.1.9.9.63.3.2.25
A collection of objects providing the GSTN (General Switched Telephony Network Voice Dial Control configuration capability. GSTN (General Switched Telephony Network), which is supposed to encompass analog, ISDN, Cellular - essentially anything circuit switched over the TDM infrastructure.
Back to CISCO-VOICE-DIAL-CONTROL-MIB MIB page.
IPHost Network monitor allows you to monitor cvCallGroupRev4 on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco firewalls right now.