I'm looking for which plist or sqlite file iOS 12.1 uses to determine which mobile device number to (attempt to) activate with iMessage and Facetime.
I have an iPhone which is trying to activate iMessage under an old phone number. The current phone number settings are correct both in the UI and in com.apple.commcenter.plist, although the latter also contains some information about old SIMs.
Doing a text search against backup images for remnants of the old phone number shows com.apple.TelephonyUtilities.plist, com.apple.commcenter.plist, and CellularUsage.db as candidates. I haven't had luck finding in-depth technical documentation on those.
I have exhaustively performed the troubleshooting steps recommended by Apple and I have an open engineering ticket. I'm specifically looking for the files where iMessage activation data are stored.