How stop "Elastic IP address not attached to a running instance per hour (prorated)"?

I am assuming that where you have mentioned delete Elastic IP is release Elastic IP. If not follow these steps.

To release an Elastic IP address

Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/. In the navigation pane, choose Elastic IPs. Select the Elastic IP address to release and choose Actions, Release Elastic IP addresses. Choose Release.

Now coming to your cost, these are might be the reasons from my experience

1. EC2 instance which is in stopped state has an EBS attached to it will incur charges
2. Other data analytics services that was provisioned but not deleted will also incur charges

You need to check in the cost explorer about the exact resource which is incurring charges. Choose "cost explorer" from the navigation menu. From Report parameters which is the right side, select "Usage Type" in Group By. You will see all the resources that are being charged including EC2-Others.

Maybe good point will delete account AWS

Are you sure you don't have Elastic IPs in a different region to what you expect? If you go into Cost Explorer you can for example group by Region and see which region the costs are coming from.

You can go to your cost explorer and select The EC2-Other category under service and group by Usage type tracking costs associated with elastic IP addresses. It will provide which region if any.