Each phone's own settings and modem file, against what that phone had before.
{ "Voice": { "EnableVolteByDefault": true }, "Signaling": { "AdditionalContactParams": { "REGISTER,INVITE,INVITE:*": "+g.3gpp.mid-call;+g.3gpp.srvcc-alerting;+g.3gpp.ps2cs-srvcc-orig-pre-alerting" }, "AdditionalHeaders": { "INVITE,INVITE:*": "Feature-Caps: *;+g.3gpp.srvcc-alerting" }, "UseIPSec": true, "IncomingCallEndReasons": { "TemporarilyUnavailable": { "StatusCode": 480, "TerminationEvent": "RemoteHangup" } } } }