I am surprised you have not had more problems using credit cards. I have had to take a couple of cab rides from IAD and both times their credit card machine "wasn't working" although it was working when I inquired prior to getting in the cab. I did get my revenge on the last one, though, fare on the meter was 58 and the credit card machine suddenly stopped working. I told him that I had 3 20's in my wallet and he was more than welcome to keep the change. This was after getting longhauled by him taking 495 to 395 instead of cutting across on the Little River Turnpike to where I live.