I have charges I don't recognise

First, if that’s a random email out of the blue it may be a phishing mail so could be nothing but a scam.

However if you have something showing up that you do not recognize you can contact apple to find out what it is and how to stop it. Sometimes these are subscriptions that people inadvertently sign up for when they install an app.

Apple Support

But the best thing to do is to contact apple directly. These forums are user to user tech support help so no one here has any access to get you an answer.

Check for the transaction here - If you see 'apple.com/bill' on your billing statement - Apple Support