18 months ago I paid a congestion charge by phone. At the time the customer service representative persuaded me to obtain a "fast track card" that would allow future payments to be made more easily. I gave all the details and waited for the card. When it finally arrived the envelope had the wrong post code while the card itself completely misspelt my name and even had the wrong registration for our car! Which means, of course, that the card and the registration number recognition system will not jibe and I could receive a huge fine!
There is good news, however. Our planned trip to London will mean arriving and departing the CGZ outside of operating hours! No charge at all!