I use MCI's online plan. 9 cents / minute anytime, 5 cents / min. Sundays; bill to credit card (= more miles); no paper bill, I receive an e-mail with a link to the site with my statement.

Out of the blue, they sent me an e-mail last week informing me that I now get 5 cents/min on Saturdays starting on Christmas. This is ongoing, not a short-term promo.

Nice move.