@Tomas Patak Welcome to Microsoft Q&A Forum, Thank you for posting your query here!
Please refer to this article: Explain how to Cancel your Azure subscription you cannot delete the azure account
Click on the Cancel subscription link from the next screen to Cancel Azure Cloud Subscription.
Click on the Yes button to cancel the subscription option, and provide the reason for deletion of the azure account then click on the button that you can able to see on the bottom of the page.
Adding more information: When you close your Microsoft account. Closing a Microsoft account deletes your Outlook mailbox, your Skype ID and contacts, your files saved in OneDrive, and your Xbox Live data and Gamer Tag. Closing your account means you won’t be able to use it to sign in to the Microsoft products and services you’ve been using. So before you close your account, take the time to tie up loose ends, cancel subscriptions, and make sure you don’t leave anything important behind—like files in your OneDrive, money from gift cards, emails in Outlook.com,
Since Azure runs on Microsoft’s identity system, you could close the associated Microsoft account. See https://support.microsoft.com/en-us/help/12412/microsoft-account-how-to-close-account
If you have a Azure AD account via your organization, the AAD admin could delete the account. If you selected the wrong country by accident, unfortunately you need to contact Azure support or sign up with a different email address.
https://support.microsoft.com/en-us/help/12412/microsoft-account-how-to-close-account or something else..
If you still have any question on cancelling the azure subscription, I would recommended for more specialized assistance on this kindly contact Azure Billing support, it's free, and it's the best choice for you.
Please let us know if you have any further queries. I’m happy to assist you further.
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