Explanation

Amazon CloudWatch is the correct service for setting up billing alerts in AWS. Here's why:

• Amazon CloudWatch allows you to monitor your AWS resources and applications in real-time. It can track AWS billing metrics and trigger alarms when certain thresholds are exceeded.
• Billing Alerts are specifically configured through CloudWatch to monitor estimated AWS charges and send notifications via Amazon SNS when costs exceed predefined limits.
• AWS Cost Explorer is primarily for analyzing and visualizing cost and usage data over time, not for real-time alerting.
• AWS Cost and Usage Report provides detailed cost and usage data for analysis and reporting purposes.
• AWS Pricing Calculator is used for estimating costs before deploying resources, not for monitoring actual billing.

The workflow for billing alerts is:

1. Enable billing alerts in the AWS Billing console
2. CloudWatch monitors the billing metrics
3. When the threshold is exceeded, CloudWatch triggers an SNS notification
4. The company receives the alert through their preferred notification channel (email, SMS, etc.)