@Muhammad Usman shaikh Thanks for reaching out. Consider this example for billing :
1) The Contoso B2C tenant has 1,000 users. 250 users are active in any given month. The subscription administrator changes from per-authentication to monthly active users (MAU) on the 10th of the month.
2) Billing for 1st-10th is billed using the per-authentication model.
If 100 users sign in during this period (1st-10th), those users are tagged as paid for the month.
3) Billing from the 10th (the effective time of transition) is billed at the MAU rate.
If an additional 150 users sign in during this period (10th-30th), only the additional 150 are billed.
The continued activity of the first 100 users doesn't impact billing for the rest of the calendar month.
There is no billing for anything else. You can read more here.
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