How do I get a refund for an unexpected iTunes charge?

Never,

First determine if it is a real charge on your account, or just a scam phishing message trying to scare you. Phishing messages falsely claiming that you have a big charge from Apple are unfortunately very common.

But if it is a real charge on your account, follow the steps in here:

If you see 'apple.com/bill' on your billing statement - Apple Support

Hello~ In addition to *ed345’s* excellent information…please se a user tip by *MrHoffman* by clicking on below and reviewing….

Billed, but you didn’t buy? - Apple Community

~Katana-San~