AT&T U-verse availability question

I got a letter in the mail advertising uverse, so I went online to look at the channel lineup, pricing, etc. When I used the availability tool online, the website told me that it wasn't available at my address. I thought that was strange since they sent me a letter, so I typed in my next door neighbor's address, and it's available there. Anyone know what the deal is with this? I couldn't call AT&T today because it was already after hours when I was doing this, but the live chat guy on the website said that "sometimes that just happens."