Refund for subscription
How can I get refund for a charge made to subscribe when it wasn’t supposed to?
iPhone XS
If you mean you cancelled its auto-renewal at least 24 hours prior to its renewal date : http://www.apple.com/support/itunes/ww (click on your country's flag, the country where you live, and which is therefore the country on the account ; click on Contact Support towards the top right ; click on Get Help under 'Talk To Us’)