If debt collectors are harassing you, you need to realize that there are laws to protect you from unscrupulous practices. The Fair Debt Collection Practices Act prohibits many of the most egregious infractions. Right now there are more and more people taking advantage of this law and actually suing and winning over debt collectors, especially the third-party collectors.
Most of the time, a creditor will try to collect a debt for a while, but most often they will actually write off the debt and sell it to a third-party collector who then tries to collect. You have the right to request a verification of the debt. The truth is that you never agreed to pay a collector for any debt; your commitment was only to the original creditor.
Check out this free website called Debtorboards.com, where you can get tips from others who have also had problems with debt collectors, about keeping paper trails, recording the harassing phone calls and even success stories about people who have asserted their consumer rights and won.
And read about The Debt Collectors Nightmare, Revenge of the Alleged Deadbeats.