Are you getting telemarketing calls from a company called Synovate? Their number will show up as 312-775-1287.
Ostensibly they are are marketing research firm. What they really are is an annoyance. They kept calling ALL of my unlisted telephone numbers, including my cell phone, daily and would not leave a message. One day I had a spare moment to pick up the phone to find out what in the world was so darn important that they felt the need to call me each and every day.
When I oh so politely explained to the heavily accented voice on the other end that I was on the Do Not Call list, the call was abruptly terminated. Apparently this is the magic bullet as they have not called me back since.
Have you registered your telephones, including cell phones with the National Do Not Call Registry? It will make your life much easier, I promise! You can also file a complaint if you received an unwanted call after your number was on the National Registry for 31 days.