Continuous harassing phone calls in reference to my husband

These "people" call continuously asking for my husband, when told he's not available at first they refused to leave any information.  They finally told me that they were calling in reference to an debt and wanted my name and information.  How they got my unlisted number is beyond me. My husband is disabled, cannot work. I have told them repeatedly to stop calling yet they persist. If this is indeed to an old debt (which he says is not, they have disclosed too much his information from his past to me. I knew nothing about this so called old debt. They need to leave me alone.