RPM Collection Agency Called repeatedly, left no messages, called early and late, wanted someone I had never heard of! Internet

For several weeks, I got harrasing phone calls from a number I did not recognize.  My cell phone was not working properly at the time, so I could not hear the voice mails that were being left.  Finally, I heard the messages, and they were from several people from RPM who asked that I call back regarding an important matter.  The first several attempts I made ended in the call being disconnected.  Finally, when I was connected to someone, I asked why I was being harrassed.  "What's the number?" I was asked.  I told her, and she said they were looking for "Nellie Winkler."  I promptly told her I had no idea who that was!  She said they were taking my number out of the system.

Here's my question: why in the world is it okay to call someone at 6:30 am and 9:00 pm and not even know if it's the person you are looking for?  I can understand persistence in making collections, but this is ridiculous, especially considering I don't owe anybody anything!  I told the woman on the phone that I understood that times are tough and jobs are hard to come by, but that I personally thought she had sold her soul to the devil.