How can I get a refund for funds added to my Apple ID ?

Funds from Apple Gift Cards in Apple ID Account are non-transferable. Do you have funds in Apple Cash account you want to transfer? Apple Account and Apple Cash Account are two different financial instruments from two different companies.

An exception to the non-transferable rule is if the funds were transferred by mistake from a bank account. The transfer can be reversed, but only to the bank that was the source of the funds.

If you need to request a reversal of an accidental transfer to your Apple ID Account, please call 1-800-MY-APPLE

You can't redeem or return Apple Gift Cards, App Store & iTunes Gift Cards or unused Apple Account balance for cash, except as required by law. If your jurisdiction allows the refund of redeemed gift balances, you can contact Apple Support to request a refund

See this link for further reference

Check your Apple Account balance - Apple Support