Billing Issue

This is the first time I have had a billing issue with another business. A printing company approached us a while ago to do targeting mailers. We are a 3D ultrasound business, and we provide services to women in their 4th-7th month of pregnancy for the most part. We were hesitant because we knew our timeframe was so tight, but they told us they could get a list of pregnant women at certain times in their pregnancy. They were listed by month. So we went ahead and did a one-time mailing with her of about 700 pregnant moms in the area who were at least 3 months from their due dates. This was in November. We have had 4 phone calls from the whole mailing, all of which were people telling me they weren't pregnant and inquiring why they received the post card. One person actually thought her identity was stolen because it was her address but not her name. We got about 4 cards back that were unable to be delivered to the sender. Basically, I think the list was horribly inaccurate. The only feedback we got indicates this, and of course then, the mailers were a giant waste of money. I understand that a few returns and inaccurate addresses is something to be expected when doing a mass mailing, so had we also gotten any business from this or actual inquiries from pregnant women, I would just accept this as the nature of this kind of marketing. However, like I said, the only feedback was from people who were not pregnant, were not named on the mailer, or from returned cards.

So, how would you handle the billing situation with this business? It's another local, small business and I don't want to screw anyone over, but I really just think the list they purchased was not what we needed and they sold it to us as credible. I have been in contact with them, and they just keep repeating that they've used this company in the past with great results (but they have never used this specific list). They basically just don't believe me or are ignoring the fact that the list was likely bad. Would you suck it up and pay in full? This is the risk of advertising? Would you try to negotiate the bill down, and if so by how much? Bottom line, I would never had chosen to do a mailing with them if I had any doubt the list was bad because, with the nature of my business, a bad list would pretty much yield 0% ROI. And it did.