I've been getting deluged with robocalls the past 3 years, but I new series of calls are downright disturbing.  Between 9-10am (usually) each day I've been getting robocalls from very similar numbers; they all have the same area code (303) and prefix (513).  Today's call was from (303) 513-1231.  I've been writing these down when I noticed this trend and  this was eighteenth DIFFERENT number using the (303) 513-xxxx pattern.  I've stopped answering these and I don't see others reporting this or similar numbers, so I find this pretty creepy.  I just block one of these after another....