I don't know why I should have paid

I understand your concern about being charged for AWS services you believe you didn't use. This is a common issue that can happen for several reasons, even when you don't think you've actively used any services.

Here are some possible explanations for unexpected charges:

1. Resources you may not be aware of: Even if you didn't actively deploy anything, some resources might have been created automatically during account setup or exploration.

2. Resources in different regions: AWS has multiple regions worldwide, and you might have resources running in a region you haven't checked.

3. Stopped but not terminated instances: Stopped EC2 instances don't incur compute charges, but their attached EBS volumes still generate storage costs.

4. Other persistent resources: Services like Elastic IP addresses, EBS volumes, snapshots, or VPC components can incur charges even when not actively used.

To address this situation:

1. You can request a refund by contacting AWS Billing Support directly. This type of support is free of charge. Open a support case under "Account and Billing" in the AWS Support Center.

2. When creating the support case, explain your situation in detail - that you weren't aware of any active services and didn't intentionally use any resources.

3. Before contacting support, it's helpful to check all AWS regions for any running resources and terminate them to prevent further charges.

AWS has been known to be customer-friendly in such situations, particularly for accounts that were intended for testing or learning purposes. While there's no guarantee of a refund, they will review your case and guide you through the process.
Sources
Free Tier account billed without usage | AWS re:Post
A charge occurred in a service that I didn't know was being maintained. | AWS re:Post
Unexpected EC2 Charges | AWS re:Post