Why did I get billed for something I’m not using

By “ not using” , what does this mean?

iif it’s regsrding an app subscription, “not using” Or deleting will not prevent charges, they need to be canceled

To manage subscriptions and turn off Automatic Renewal, follow the instructions here:

View, change, or cancel your subscriptions - Apple Support

If you see 'itunes.com/bill' or an unfamiliar charge on your statement

https://support.apple.com/en-us/HT201382

And check your purchase history to see what you’ve bought