Every month, the billing system analyzes your monthly voice and data usage, then suggests the most appropriate plan and/or add-ons based on your needs.
If you are using more data/voice/features than your current plan offers, you would receive an email alert recommending certain add-ons, or to upgrade your plan for the next month. Conversely, If you were using much less, the email would recommend that you downgrade plans, or get rid of certain add-ons. Emails should also alert current customers when new plans are launched that might better suit their needs.
This would ensure that customers are not unintentionally overpaying for service, and they can feel more empowered in their decisions when choosing or changing plans.