Employer Refusal to Pay Bills?

Some colleagues of mine and I recently worked on a political campaign in New Hampshire. During that time, with authorization, part of our job was to rent/purchase various supplies (GPS units, etc.) The campaign is now (after the campaign is over) claiming that we are personally responsible for these bills. It seems ridiculous to me. Any guidance on law anyone has so that we can resolve this situation would be appreciated. (Incidentally, they also haven't paid us what we're owed.)