I've had a similar problem, though it wasn't lead quality.
I sent some traffic to NeverBlue back in the day on this niche rebill offer for women. The advertiser was rather new and didn't have their backend set up correctly and their pixel was double/triple firing on all my leads. After about a week, NB informed me they couldn't pay me because of the advertisers mistake and would only pay me for my costs involved.
I accepted it as NB told me this would NOT happen again and if it did I would be paid fully 100%. The advertiser told NB they corrected the problem and I again started running traffic again for another week and guess what? Same issue. NB contacted me and said they would only pay me traffic costs again.
Not only did feel I was lied to, but when I send in proof of my traffic costs with a CSV and screen shots, they questioned the amount I spent on traffic saying it was rather high ( i was working on slim margins anyways to begin with ), and I had to justify every penny spent on my traffic with them.
To add insult to all this, it took them almost a solid month and a half to even pay me, even though I was set up on weeklies with them which I confirmed with my rep. I kept getting the old "check is in the mail" bit for about 6-7 weeks.
When I finally did get paid, it was not the agreed amount me and my rep came up with for my traffic costs ( it was lower ).
To this day, I wont run any traffic with them whatsoever.