I deleted an app and emptied the trash. When I went to the App Store it was there with the open button. I don't want the app because it charges you by the week or month. How do I completely uninstall it?

Subscription apps will continue to charge you even if you have removed them. You need to cancel your subscription with that specific application vendor.

I have two comments to offer. First, sometimes, when moving an app to the Trash, not all of the app's bits and pieces are always removed. When possible, it is better to use the app's uninstaller, if one is available, to completely remove it. Second, when looking at the App Store, it is showing the app's you have previously downloaded. It has no bearing on what may or may not be installed in your computer at the time. If you click on the open button, it would reinstall the app. If you do not, it will not.

Start by going to the Developer of this App website for specific instructions on how to remove their App