A. Compare the WAN bandwidth usage during call setup and active call phases to determine if there are any bandwidth limitations.

B. Configure a VPN connection to the remote site to bypass WAN congestion and improve voice quality.

C. Perform a packet capture and analysis of the WAN traffic using a network analyzer tool.

D. Enable and monitor SNMP traps on the WAN routers to detect any network or connectivity issues.

E. Check the network performance metrics, such as latency and round-trip time, to identify any abnormal values.