Near the end of the scene in Taxi Driver where Travis takes Betsy to the porn movie, after she leaves angrily for her home in a taxi, he says, "Jesus Christ, I got a taxi". He didn't bring his taxi, as it was his day off when he took her to the movie. They come walking to the movie. What was he referring to?
I think Travis was confused about Betsy's decision to leave in a cab. Travis thought of Betsy as being classy, and probably decided to walk her to the movie rather than bring her in his cab because he thought it was "beneath" her to ride in one. When she left in a cab, his reaction was one of surprise, both at her leaving and at her leaving in a cab.