404 pages without a trailing /

This isn’t totally a wordpress question but i’m sure one of you will know the answer.

when i direct my browser to https://www.ciccarelli.biz/anythingNOTavailable/
with a trailing slash, i get my 404 page as i should

but when i attempt to go to https://www.ciccarelli.biz/anythingNOTavailable with no trailing slash, i get a index of my entire server…anyway i can change this so i get the same results? i DEF do not want a directory listing when someone enters an address with no trailing slash because i run multiple websites off this server and its the same result on every domain, maybe something i can do in .htaccess files? i am totally clueless on how to approach this, and my webhost offers 0 support for this type of thing, they are total assholes. they basically tell me to google for help, its actually rather funny.

thanks in advance!

NOTE: anythingNOTavailable is not actually a directory or file, just the term i used for something thats not there, i coulda used “jksdfsdf” or anything else thats, not physically there.