Who do I contact about iTunes charges I never made?

See each of the steps in the following instructions. They include information on contacting Apple Support if the other steps don't help: https://support.apple.com/en-us/HT201382

If the only indication of the charges is from an email or text, be aware that it may be a phishing attempt to get you to log in to a site that appears to be Apple and divulge your password or credit card information. See: https://support.apple.com/en-us/HT204759

and https://support.apple.com/en-us/HT201679