Create OnlineMeeting in MS Graph with Call-in Info - microsoft-graph-api

Question

I am building some utilities to automate aspects of Microsoft Teams at my company. One thing we are trying is automating scheduling/creation of Online Meetings under various circumstances. Overall this is working fine, but I can't figure out how to get / attach telephone call-in information for the calls we're creating.
Here's an example POST /app/onlineMeetings:
{
"meetingType": "meetNow",
"participants": {
"organizer": {
"identity": {
"user": {
"id": "<user-id>"
}
}
}
},
"subject": "Personal Room"
}
And here's what a typical response looks like:
{
"#odata.context": "https://graph.microsoft.com/beta/$metadata#app/onlineMeetings/$entity",
"joinUrl": "<join-url>",
"subject": "Personal Room",
"isCancelled": false,
"meetingType": "MeetNow",
"accessLevel": "SameEnterprise",
"id": "<meeting-id>",
"audioConferencing": null,
"meetingInfo": null,
"participants": {
"organizer": {
"upn": "<user-name>",
"sipProxyAddress": "<user-name>",
"identity": {
}
},
"attendees": []
},
"chatInfo": {}
}
As you can see, the audioConferencing key is null. If a user accesses the joinUrl, they can join the call and audio conferencing information is displayed at that time -- but I can't figure out how to get it out in advance (e.g. to send in an email).
Also note that since this is not a VTC-enabled meeting, the id can't be used to issue a new GET request for additional information, as discussed here