I would have to agree with the sentiments of previous posters regarding this issue. None of us enjoy being taking for a ride, but more times than not going public with it might not be the best resolution.
From the legal standpoint Pucks question about the contract is very valid – was an insertion order placed? Have you documented previous attempts to resolve the issue?
If all else fails as a last resort I would recommend that you take your dispute to the free for all area here at CAP, with evidence in hand and have at them.
Best of luck.