Continued harassment by phone and mail

They keep calling and sending me notices about some car I've never owned. I've never owned a BMW, but they even include some fake vehicle code for "my 2011 BMW". Man called me and actually argued with me that his records show that I have a BMW with an expired warranty. Correspondence by mail is made to resemble a cancellation notice. They actually tell me I must call them and verify that I have a current warranty. This bunch needs to be shut down. They are a menace and will not stop.