Account info sold??

I work for a small govermental agency that just setup Comcast service in another building that we have equipment in.  Our agency has no affiliation with this building; the service address with Comcast is the first and only time our name and this address came together - yet - we recieved junkmail to our agency at this service address!  Where did we consent to having out information sold or given out?  The only explanitation I can come up with is our name and this address (only known by Comcast) was distrubuted to a third party. 

How do we stop this and have it removed?  The address in question is our city's Police Headquarters, and they would appreciate it if mail to us stopped coming to their facility.