They can't simply "get a warrant." What they can do is1 If you were paid for hours you did not work, you are not entitled to the money. They may sue you to get it back--i.e. they can file a lawsuit in the appropriate court against you.2 If you caused the overpayment intentionally, such as by lying about or falsying the hours worked, you committed a crime--a form of theft--and they can file a police report and look to press charges against you.3 They can of course fire you.So while they can't simply "get a warrant" in 72 hours, there are serious things they can do. Your best bet is to talk with them and see if you can enter into a payment plan to repay the money over time you should try to be as aggressive about payment as you can be, and repay in as short a time as possible. However, they don't have to agree to a plan--it's voluntary on their part--so they could insist on full payment or they will sue you, etc.