Easiest way just go on Twitter and tweet support. You'll get a response asap. Second way look at all the emails you've ever received from uber and look for a account Id, like a 16 character code. Its not published, look at the links or the reply to address. I had one on a old PW reset. That's your account Id. Forward that message and state the Id to support and tell then you were hacked.
Edit: FYI check out
https://gimletmedia.com/episode/91-the-russian-passenger/
Its a podcast where they talk about uber account hacking. Tldr: anytime there's a hack and passwords are released. Hackers will try that email and PW on uber and if you use common passwords your toast.
Best bet is ask for help on twitter, its public they'll answer.
Second edit:
Call your credit card company and tell them to deny all uber charges if they can. Most likely its best to get a new card just to be safe.he
