How to find out my case ID or patch ID

I am trying to report refund issue to Apple support team via Apple Support, however I do not know how to find out case ID, I tried using Order ID (DOCUMENT NO) in the 'enter the case ID or patch ID ' and using my last name in the second tab ' last name ' but I am getting error:

'We can't find the case

The case ID and last name do not match the information in our records. Please check the information provided and try again. The case ID can also be found in the confirmation message from Apple.

Please try again'

Can you please advice how can I resolve this problem?

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