charges

Look at this, If you see 'apple.com/bill' or an unfamiliar charge on your statement - Apple Support or this, Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

Apple sends you an email receipt for every purchase you make. Did you get an email?

No? It's a scam.

I get a receipt but I don’t know what it is for

It may be a phishing attempt to get your account info. Do not click on any link in there, and look at the link I provided regarding phishing messages.