Call repeatedly and disconnects without message when answering machine picks up

Call private, non-published numbers on office phone system repeatedly and disconnects without message when voice mail picks up. Reverse trace runs back to :      
     
      Mark Facey & Company
      Jeff Neistat, VP, CFO
      860-589-0221
     225 North Main Street
     Bristol, CT 06010
     Phone: 800-237-0938
     Facsimile: 860-589-9128
     Web: markfacey.com