My son purchased an app subscription that we would not have approved had we known it was going to cost $$$. We are hoping we could get a refund and cancel subscription

My son purchased an app subscription that we would not have approved had we known it was going to cost $$$. We are hoping we could get a refund and cancel a subscription. I have NO CLUE on how to communicate with Apple to do this. I was sent some links and when I request refunds it doesn't give the option for apps only my iCloud stuff like when I paid for more memory and when I renewed.