There’s a few different ways to go here and a lot depends on your jurisdiction (presumably Europe?) but this feels like wage theft. I’m sure Upwork has armies

There’s a few different ways to go here and a lot depends on your jurisdiction (presumably Europe?) but this feels like wage theft. I’m sure Upwork has armies of lawyers who would argue that you’re an actual business and this is a business to business dispute. And I’m sure you accepted some 78 page document that says that too. But unless you have an incorporated entity and are operating like a business I’m not so sure a regulator would see it that way. There’s a lot of laws out there involving freelance workers, subcontractors, and so on, and I’d figure out which of them apply to you. Also like others have said you don’t owe them anything don’t do more work on Upwork to pay off this “debt” fuck that. And also chargebacks in the US at least have strict time limits, so the amount of delay here in informing you seems relevant. But not sure what the rules are where you are.