"To dispute the debt" means to disagree or challenge the existence or validity of the owed money. It involves raising concerns or doubts about the amount of debt or questioning if it is owed at all. Full definition
Dispute the debt with the credit reporting agencies based upon a factual error. (rebuildcreditscores.com)
It is best to dispute a debt collection as soon as possible, generally within 30 days of when you were first contacted by the agency. (ovationcredit.com)
Once you receive the written notice, you have a 30 - day window to dispute the debt in writing. (debt.org)