I would like a refund of $9.99 for Apple iTunes purchase I did not want. The Apple iTunes purchase was not authorized by me.

You do not say where you see this purchase. If it is an e-mail or text message are you sure it is real and not an attempt to steal your private information ('phishing') (very common)?

Phishing & Other Suspicious Emails - https://www.apple.com/legal/more-resources/phishing/

Identifying legitimate emails from the iTunes Store - http://support.apple.com/kb/HT2075 (the previous link is more specific)

Forward attempts to: reportphishing@apple.com

If you still think the charge is real:

See your purchase history in the App Store or iTunes Store [iOS, computer, or web] - Does not include purchases made by others under Family Sharing; those have to be checked from their accounts.

http://support.apple.com/HT204088

If you see ‘itunes.com/bill‘ or an unfamiliar charge on your bank, credit card, or debit statement - https://support.apple.com/HT201382 - "Before you contact Apple to request a refund for a charge you don't recognize"...

If neither you nor a family member (if applicable) has a record of this purchase and you only saw it on a statement for a card you alone control, contact your bank or card company about card fraud. Apple does not handle that.

If you do now recognize this purchase and are asking for a refund then realize Apple's terms of purchase for most countries are effectively, "All Transactions are final" (check terms at: http://www.apple.com/legal/internet-services/itunes/). Apple does refund on a case by case basis, but they can also refuse.

Request a refund for an App Store or iTunes Store purchase - https://support.apple.com/HT204084

Report a Problem - http://reportaproblem.apple.com - "Sign In for help with iTunes purchases made in the last 90 days"

If a reporting a problem request is unsuccessful you can also try:

Other ways to contact iTunes Support:

https://www.apple.com/emea/support/itunes/contact.html

or

https://support.apple.com/country-selector/itunes

I am just a product user like you, not Apple. Follow the instructions I provided in the post and the links. Have you verified this is indeed something charged by Apple and not bank fraud? Do not report fraud until you are certain this is taking place. Are you the organizer for a Family Sharing group? It could be another person in the group (I really have posted all this already…)

$9.99 sound like a typical Apple Music subscription amount. Apple always tries to get you to sign up for AM and you may have just clicked on "agree" to everything in front of you at some stage. You get a 3 month free trial then it rolls over to a paid subscription, and you may be seeing that. If that is the case: Manage your Apple Music membership - Apple Support - https://support.apple.com/HT204939