What is AWS Support (Developer) charges for free tier account ?

Hello.

"AWS Support (Developer)" is the AWS support fee.
The AWS Support Developer Plan is not included in the free tier.
The developer plan is a plan that will cost you at least $29.00.
The developer support plan is billed at the higher of $29 or 3% of the AWS monthly fee.
https://aws.amazon.com/premiumsupport/pricing/?nc1=h_ls

If you want to stop using "AWS Support (Developer)", you need to change the support plan to the basic plan (free).
To change from the Developer Plan to the Basic Plan, sign in to your AWS account as a root user.
To sign in as the root user, follow the steps in the document below.
The root user can perform all operations within the AWS account, so please be careful when operating.
https://docs.aws.amazon.com/signin/latest/userguide/introduction-to-root-user-sign-in-tutorial.html

After signing in as a root user, please follow the steps in the document below to change your support plan.
https://docs.aws.amazon.com/awssupport/latest/user/changing-support-plans.html