If you make it clear to the debt collector that you dispute the debt that they say you owe, then they may not contact you anymore until the dispute is resolved. If in fact the collector does contact you about the debt after such a dispute is made (but before it has been resolved), the collector has violated your consumer rights. If it can be shown that this happened, then you stand to receive an award of damages from the creditor.
The area of law that covers this particular subject is the Fair Debt Collection Practices Act (FDCPA). This is a federal statute that regulates what a collection agency may or may not do in their attempts to collect on a debt. Section 809(b) of the law states: “If the consumer notifies the debt collector in writing within thirty (30) days that the debt, or any portion thereof, is disputed, or that the consumer requests the name and address of the original creditor, the debt collector shall cease collection of the debt… until the debt collector obtains verification of the debt or any copy of the judgment.”
So if a collection agency contacts you about a debt, and you dispute the validity of it (in writing, or by making this dispute clear over the phone), then the collector has to cease all collection activity until the debt is verified. This means that the collector must provide you with some sort of documentation proving that the debt exists. But very often (for whatever reason), the collector will continue calling and harassing you during this period (before they provide you with any document proving the validity). It is on those occasions that a violation occurs.