someone has my account info and is purchasing things. how do i stop and report this

Change your Apple ID password https://support.apple.com/en-us/HT201355

See What to do after you change your Apple ID or passwordhttps://support.apple.com/en-us/HT205064)

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See these security documents:

If you think your Apple ID has been compromised https://support.apple.com/en-us/HT204145

Security and your Apple ID https://support.apple.com/en-us/HT201303

iCloud security overview  https://support.apple.com/en-us/HT202303

Ways to keep your information safe on Mac https://support.apple.com/en-gb/guide/mac-help/mh11402/mac

Using app-specific passwords https://support.apple.com/en-us/HT204397

UseTwo-factor authentication for Apple ID https://support.apple.com/en-us/HT204915

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If you already are using two-factor authentication, Check your Apple ID device list (https://support.apple.com/en-us/HT205064) and remove any device that shouldn't be signed in using the steps in the link.

After securing your account, contact iTunes Support for assistance. See the Apple Support article below for contact information.   

iTunes Support – world wide        

Normally, all sales are considered final, but you can ask for a refund.

If you have received a confirmation email, click the Report a problem link at the bottom.

Purchases problem.      

How long refunds from the App Store or other Apple services take.