Our current setup handles incoming differently than ViaTalk, so it's just not really possible.

With ViaTalk, they have the calls directly going to their SIP servers and have the full headers, etc.

With our setup, incoming calls go to core routing servers to be normalized and then sent to the appropriate SIP server based on where they customer is registered dynamically. So the SIP servers themselves where the features are handled don't have the raw headers from the original call to work with.

Our method is a lot more scalable, but there are definitely cons to it like this as well.