With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
csbHistoryStatsActiveCalls
Cisco Session Border History Stats Active Calls
1.3.6.1.4.1.9.9.657.1.4.1.3
This object indicates the number of active calls history during this interval.
Back to CISCO-SESS-BORDER-CTRLR-CALL-STATS-MIB MIB page.
IPHost Network monitor allows you to monitor csbHistoryStatsActiveCalls on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco wireless switches right now.