Charges on Free Tier Account

Hello.

Could you please show me a picture of the invoice?
You need to check which part of the VPC category is incurring charges.
https://us-east-1.console.aws.amazon.com/billing/home#/bills

Also, did you create any resources other than VPC?
For example, do you create EC2 and have a public IPv4 address attached?
Public IPv4 addresses are charged, so if you create some AWS resource and have a public IPv4 address attached, you may be charged as a VPC fee.

Can You share screen shot of your issue. We'll get more clearity what happen with your account.

Okay You mention you seeing WAF fees, right! AWS WAF is web ACl and this service is not included in AWS free tier. This might charge you for creating it or making web process request. https://aws.amazon.com/waf/pricing/

Better you should look into products and services that are mention in AWS free tier.https://aws.amazon.com/free/?all-free-tier.sort-by=item.additionalFields.SortRank&all-free-tier.sort-order=asc&awsf.Free%20Tier%20Types=*all&awsf.Free%20Tier%20Categories=*all#Learn_more_about_AWS_Free_Tier_Products