I'm currently working on upgrading our custom app from v12 API to v15 and have noticed the following in the documentation: HistoryIDOfTheCall: Obsolete. Each call has unique history ID. It is persistent unique ID of the call in call history database. (obsolete) v14 - call history database does use this ID. We make extensive use of this as we follow a call from when it first arrives in our system and then as it's transferred between multiple IVR / receptionists. Is there a suitable replacement which allows us to go all the way through the system?