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I understand your concern about unexpected charges for Amazon ElastiCache. Let me provide some information that might help clarify the situation.

Amazon ElastiCache charges are based on the resources you provision, such as cache nodes, and you pay for the hours these resources are running. Even if you don't actively use the service, as long as the resources are provisioned, charges will accrue.

If you created an ElastiCache cluster for learning purposes and didn't delete it properly, charges would continue to accumulate. ElastiCache pricing works on an hourly basis for on-demand nodes, and you're charged for the memory capacity by the hour.

It's worth noting that there are no ElastiCache data transfer charges for traffic within the same Availability Zone (AZ), but standard EC2 data transfer charges apply when transferring data between different AZs in the same Region.

To address your current situation:

1. Double-check all AWS regions in the ElastiCache console to ensure no resources are still running (resources might exist in a different region than the one you're currently viewing).

2. Check your AWS Cost Explorer or billing dashboard to identify exactly when the charges started and in which region.

3. For refund consideration, I recommend contacting AWS Support directly. AWS has a customer service team that can review your specific case and billing history.

For future reference, if you're learning AWS services, consider using the AWS Free Tier offerings. ElastiCache offers 750 hours of cache.t3.micro node usage free for up to 12 months for eligible accounts.
Sources
Pricing for Amazon ElastiCache