Billing appear in March

You can go to your account and click bills which will show you the resources you used, the duration and the associated costs. You can also check cost explorer and click monthly or daily view.

If you can't find the resources then check out this link https://aws.amazon.com/premiumsupport/knowledge-center/resources-unexpected-charges/.

Once you found out the resources, you need to terminate them all manually yourself. I don't think there is any shortcut to terminate all resources generating those charges.