Why does comcast not install service on the date as promised?

I ordered comcast service over the internet and was promised an install date of 1/23/10 between 8-11am. When no one showed up I called comcast and they had a date of 1/28/10 in their system. I have a confirmation for a sales rep telling me 1/23/10. This is ridiculous.

here is the transcript: (the important part)

Angela(Wed Jan 20 2010 21:15:51 GMT-0500 (Eastern Standard Time))>

Okay, I will reserve the 23rd schedule between 8-11am.

James_(Wed Jan 20 2010 21:15:56 GMT-0500 (Eastern Standard Time))>

fantastic news

Angela(Wed Jan 20 2010 21:15:58 GMT-0500 (Eastern Standard Time))>

Your order confirmation number is 016383744579. Your monthly bill will be $74.95 plus the one-time installation fee of $29.95

What can I do!!? Come on comcast, it's my sons first birthday and I had to take off work!!