Your bank. You dispute the charge. Uber can deal with your bank. It doesn't matter it was a debit card. It means you're missing the money immediately, but doesn't stop you from disputing.
I would say, sending uber an email would work, or calling their number (which, they actually do - if you lost a phone in an uber, they have a number which lets you call them to get the contact details of the driver of the car you were in).
So it only applies to chargebacks of transactions you've previously authorized, not for fraudulent unauthorized charges.
If I took an Uber (or attempted to take an Uber) and I had a dispute with them about payment = attempt to work it out with Uber first.
If I didn't take an Uber at all = contact bank.
Is the convenience of an app so important to you that you're willing to deal with this nonsense?
Wait until Uber is the only option for a ride across town. Now what?
If you are a driver, a ban seems more permanent, but it's not like they really identify riders.