SUB CO Inc Unsolicited magazine subscriptions unknown, Nationwide

For some time I have received unsolicited magazine subscriptions from Sports Illustrated, Entertainment Magazine, and others.  I have called the magazines to find out who signed me up but they refer me to Sub Co, Inc who I have been unable to get a response from.  I wish to be taken off what ever it is they are using to authorize these subscriptions and find out who started it in the first place.  Anyone with a good idea on how to do this?  What a rip off.  I wonder when the bill will come.