Hi @Phạm Trường
Thanks for reaching out! All of our billing models are based on consumption (except for phone numbers). For Voice and Video calling we bill based on minutes per user (i.e. three users in a call for ten minutes would result in thirty minutes of billable usage). The other core services within Azure Communication Services also follow the same model (per message or per minute rate). Phone numbers have an additional monthly cost for owning the phone number.
You can find more details on our pricing here: https://learn.microsoft.com/azure/communication-services/concepts/pricing
Hope this helps!