How can I get the invoice of a purchase I made in an Apple shop?

Yeah I know, they didn't pick up my call before :D. But I contacted Apple support and they called the store and transferred the call when they answered.

They usually help in those matters, tell them I can't reach Apple store.

Contact - Official Apple Support

Also have you checked your Junk mailbox?

Better to contact the Apple store where you bought your item from.

Try pressing the bag shown here toward the top of Apple’s website. Then choose “Orders” from the dropdown.