The subscription updated notification is sent when a subscription is updated using either the self-service account management or in the Billsby app.
{
"SubscriptionUniqueId": "M6JYJRPV4Q",
"CustomerUniqueId": "QV4WNSL7E6",
"SubscriptionStatus": "Active",
"BillsbyProductId": 50,
"BillsbyPlanId": 155,
"BillsbyCycleId": 217,
"Units": 1,
"NextBillingDate": "2020-06-22T10:17:42.018276",
"Type": "SubscriptionUpdated",
"Id": "070406cd-b4c5-4589-a546-4ca97bb6ed09"
}