The U.S. Bankruptcy Code states that once a debt has been discharged, no attempts may be made to collect on that debt. Unfortunately, it is not uncommon for unethical creditors and collections agencies to continue attempts to collect.
There are a few things to be aware of should you ever find yourself being hounded because of a debt that you no longer have any legal responsibility to pay.
From time to time, a creditor will sell an account that has been discharged in bankruptcy. The new owner of the debt will then attempt to collect from you. This is clearly illegal.