Because you're dealing with a D- Book--obviously. I get it because I have dealt with this situation a few times before, most recently with 1 Vice (and it eventually worked out where I recovered my full 12k). What I would do is respond to their email and get on a payment plan with them for your remaining balance. They have admitted in writing to owing your balance and a goal to settle it w/i the next 3 months. So ask them how they plan on accomplishing this, and keep them to this schedule via pressure with SBR (assuming you filed a complaint with them). Until then, I would tone down the thievery rhetoric as it could only hurt. Right now it's "only" a slow-pay situation. Just my 2 cents.
Hope it all works out