PHX-DEN on the return two things happened. First I was asked for my ID which I have never gotten in all my years of flying. My aging cream must be really working. And then the FA tried to charge me for a double, but at the single price, which I'm confused across the board because she selected my seat on the pad which should have my info? I reminded her about the MCE initiative and she immediately went, "oh ya, right" told her other FA and continued on.