If I understand correctly, I think you don't need to make your own API calls to get the "order" details.
If you mean to query the purchases for Google in-app billing,
B4X:
Wait For (billing.ConnectIfNeeded) Billing_Connected (Result As BillingResult)
If Result.IsSuccess Then
Wait For (billing.QueryPurchases("inapp")) Billing_PurchasesQueryCompleted (Result As BillingResult, Purchases As List)
Log("Query completed: " & Result.IsSuccess)
Google has deprecated the previous method of sending push notifications. It will stop working on June 2024. If you have an already working solution then you only need to update the B4J side. Do make sure that you switched from the service to a receiver on B4A. The new API is (confusingly) named...