Make rate responce mandatory for call (per_minute).
Add 4 options inbound_rate_required/outbound_rate_required (default false) and inbound_rate_resp_timeout/outbound_rate_resp_timeoutto (default 10000) to system_config/ecallmgr database.
When *_rate_required set to true then call after authz ecallmgr wait for *_rate_resp_timeout and if no rate responce received then this channel killed.