Free voicemail greetings

I bought a donut and they gave me a receipt for the donut. I don't need a receipt for a donut. I just give you the money. You give me the donut and the transaction. We don't need to bring ink and paper into this. I just can't imagine a scenario where I had to prove that I bought a donut. Some skeptical friends don't even act like I didn't get that donut. I got the documentation right here.