So... I asked Uber to change the card for a trip, which they dutifully did and which has ended up in a bit of a customer service nightmare. Basically their system double-charged the new card, and it seems it is now trying to charge me a "negative" amount, which will not go through to any card, rendering my account unusable.

Customer "service" has meant 6 emails with 5 (going on 6) agents who, despite copious documentation, each seem to believe I have an outstanding balance on my account. (It shows up as a negative amount of my double charge when I log in to uber.com.)

Has anyone else experienced something similar? Any hints for how to deal with them? At this point I've just disputed the charge.