I called Discount Tire today, and it was them who made the mistake. I was thinking it would not have been their mistake, but sure enough, it was. No problem for me - they installed the correct tires this morning. Problem for the guy who was supposed to have the 275s. Discount Tire said it was an expensive mistake on their part, so I'm assuming they are going own up to their mistake and tell the guy. I had driven about 50 miles on them. Doesn't look like there is any damage to my car.