What's the proper way to release a subcontractor?
It's also an opportunity for you to ask for the return of any of your company property--or in this case, for the contractor to "cease and desist" his use of your property.
If he refuses (or doesn't comply), you may need to take the step of getting an attorney involved. The Digital Millennium Copyright Act also permits you to notify the contractor's internet service provider that the contractor has infringing materials (your logo, etc.) on his site and to request that the site be taken down.
Going forward, you may want to have a written agreement with your contractors outlining your expectations when situations like this occur.