Why do I use the free plan, but still incur charges？

Why do I use the free plan, but still incur charges？

This is difficult to answer without some more information about the resources that you're using, because there may be several reasons that you're being charged. For example, you can use Amazon EC2 to create a free t2.micro instance. However, if you transfer more than 10 TB from your instance out to the internet in a month, you pay a fee for each additional GB. If you use more than one Elastic IP, you are charged for each IP beyond the first. There are several variables that can result in you getting billed.

I recommend that you set up a spending alarm to notify you when you exceed your free tier allowances. Also, consult the pricing page for each AWS service that you use in order to understand what is included in the free tier and what isn't. Finally, you can use the Billing Dashboard to understand where your charges are coming from, and see an estimate of your monthly bill based on your usage trends.

And how can I get AWS human customer service？

If you have questions about billing, open a Billing case in the AWS Support Center.

Thanks BrentAtAWS - I will think of creating a spending alarm as well