ORIGINAL BILL FOR MY SECONDHAND IPHONE 12 PRO

That’s unlikely.

You can check the warranty status here: Check Your Service and Support Coverage - Apple Support

In most countries, the original receipt is not required for service. The warranty is only valid in the country where the device was originally sold.

You would have to contact the person / store that you purchased the secondhand iPhone from.

Axel F.

Nothing. You can not get the original receipt for something which you did not originally purchase.

No.

Ask you money back from the the shopkeeper, perhaps you have bought a stolen iPhone.

If you can't get in touch with the previous owner, you can't use the iPhone.

👉 Read this before you buy a 2nd hand iPhone.

Why do you think you need the original bill for the phone?