...
When enabled, customers will be able to configure email alerts that we can automatically send to them, if one of their Pay-as-you-go service renewal invoice total will hit user-defined threshold.
This way customer can react, trim resources to prevent from unexpected big invoice.
How it works? - Staff Perspective
...
Additionally to customer alerts, Billing Alerts module can automatically issue invoice for customer Metered/Bandwidth-billed service before regular renewal date, if total amount of upcoming invoice reaches certain threshold/amount. This way you can protect yourself with customers consuming a lot of resources and not paying you at the end of month.
Installing module
...