It is possible for the system to permit a CLI that is not recognized by the VOIP LOGIN (digest authentication) during the incoming call.  

The "Trust CLI" option has been implemented to avoid the '403 Authentication Failed' error in cases where the CLI does not match the VoIP login.

If the Trust CLI option is disabled, and the CLI does not match the Account name, the call will be rejected.

Once the Trust CLI option has been enabled, the CLI can be different from the Account's name and the call will not be rejected.