Get rid of bats - how?

Check whether you're allowed to before anything else. In the UK all bats are protected and you can't disturb a roost without getting advice first, and a lot of US states restrict removal in summer when the young can't fly yet. The legal method is exclusion: watch at dusk to see where they come out, fit a one-way exclusion device over that gap so they can leave but not get back in, and seal every other gap. Spring or autumn, never while there are young inside.