Accidentally adding money to Apple account.

If you mean you have add funds to your Apple Account balance, you need to contact Apple Support to request a refund, see -> Check your Apple Account balance

Check your Apple Account balance – Apple Support (UK)

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If you have an Apple Account balance that you can’t use

• You can't redeem or return Apple Gift Cards, App Store & iTunes Gift Cards or unused Apple ID 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. 

When you contact Apple, include the following information:

•               Your Apple ID.

•               The refund amount.

•               Your current delivery address.