Explanation
Create budgets to manage costs and create alerts that automatically notify you are your stakeholders of spending anomalies and overspending.
To set it up, go to the Azure Portal, select 'Cost Management + Billing' -> 'Cost Management' -> 'Go to Cost Management'.

Note: Cost alerts are automatically generated based when Azure resources are consumed. Alerts show all active cost management and billing alerts together in one place. When your consumption reaches a given threshold, alerts are generated by Cost Management. There are three types of cost alerts: budget alerts, credit alerts, and department spending quota alerts.
Reference:
https://docs.microsoft.com/en-us/azure/cost-management-billing/manage/getting-started