...
Next step to verify that your communications are secure will be to take a packet capture either by port mirroring on switch level if you are using just hard phones or launching a Wireshark capture on the PC where softphone is installed.
Warning: Using TLS/SRTP may introduce interoperability issues between SBCs, gateways, and phones. Its use may break certain call features such as Bridged Line Appearance (BLA) / Shared Line Appearance (SLA), or introduce issues with call scenarios such as conferencing and call transfers.
Note: Polycom does not support wild-card certificates
...