Mundomedia refuses to pay 11.5k $

Hello everyone, until this moment I was in read-only mode and I apologize that I have to post my first thread with a problem.

I was faced with the fact that Mundomedia refuses to pay me 11.5k $.

In November-December 2017, I began to send native traffic to casino offers on a recommendation from my AM.
Before that, AM successfully approved my lander.
I sent a lot of traffic to these offers from Revcontent and Mgid traffic sources with the final result in a small minus on the ROI and eventually dropped it and focused on other things that I can do better.
During this time, I did not receive any complaints about the quality ...