ARE CHECKS A LEGAL CONTRACT/TEXAS

WE RECENTLY MOVED AND HIRED SOME MOVERS TO COME MOVE OUR STUFF AT $100/HOUR FOR 3 GUYS. TO MAKE A LONG STORY SHORT, I CALLED AND COMPLAINED THAT ONE OF THEM WAS NOT WORKING AT ALL AND IT WAS TAKING A LOT LONGER THAN EXPECTED. WE AGREED THAT I WOULD PAY FOR 8 HOURS INSTEAD OF THE 10 THAT IT TOOK, BUT THEY TOLD ME THAT WE HAD TO SIGN FOR 10 HOURS AND THAT THEY WOULD ADJUST IT IN THE OFFICE (I KNOW THAT WAS STUPID, BUT WE DID IT). ON OUR CHECK FOR $800 WE WROTE "FINAL pAYMENT" IN THE MEMO SECTION AND THEY HAVE CASHED THE CHECK. NOW THEY HAVE SENT OUR BILL TO A COLLECTIONS AGENCY. I KNOW IT IS ONLY $200 AND A LOT OF PEOPLE WOULD JUST SAY PAY IT AND GET IT OVER WITH, BUT IT IS THE PRINCIPLE OF IT THAT GETS ME. FIRST THEY LIED ABOUT ADJUSTING THE BILL AND THEY OFFER 3 GUYS TO MOVE AND ONLY BRING 2 WORKERS.

ANY SUGGESTIONS???