Unfortunately, customer service support has always been notoriously difficult to get from Uber. Now, by withdrawing from offering all help via phone or email, they've actually made it harder to get help when you need it. And it's even more difficult if you're not one of their registered customers.
Say an unexpected charge shows up on your credit card from Uber. As a first line of defense, call your credit card company ASAP and dispute the charge. Your credit card company will then ask Uber for documentation of the charge. If Uber can't produce this documentation, the charge should be removed from your credit card account. This process takes time, so it's recommended that you do this as soon as you notice the charge on your card.
You can then try calling Uber at (800) 353-UBER, although by all reports, you will never get to speak to an actual human being or get any satisfactory resolution over the phone.
One channel you might try using to get a response from Uber is to post something to their Facebook page or Twitter account. Posting on social media will sometimes get the attention of big corporations like Uber, since these online reviews are public and will hurt their reputation. If you don't have Facebook or Twitter, find a friend who does, and ask them to help you! Sadly, these indirect methods are most likely your best bets for getting the issue resolved via Uber.
If you actually are an Uber customer, you can read this article on our website to learn more about getting help from the company via the smartphone app or via their website. Even for their own customers, Uber no longer offers customer service via phone or email; you must request help via the app. Tough luck for users who are having trouble logging into their Uber account or whose phones are having problems.
Let us know in the comments what your experience with Uber customer service has been, what you tried, and whether you were satisfied with the result!