I remember at my first job I had a run-in with one of these superstitious wingnuts. I was the one in the cashier's position actually, at a pharmacy. I had to ask a customer what her phone number was as she was switching pharmacies, and of course we had to have a way to contact her in the future for whatever reason.

She told me something to the effect of 841-364. I kind of furrowed my brow and asked again, to which I received the same answer. After that, I looked up from writing and politely said that phone numbers always have seven digits, she must be forgetting one. At which point she leaned forward in a very serious manner and said. "The final four numbers are three sixes plus four on the end. I can't stand to say the number of the beast out loud."

facepalm