Non Payment from a 3rd Party company

I am a contractor out of South Carolina and we do a large range of service calls through leads we get from the Handy Technologies company, however we have not been paid for many many jobs that have been completed. They try saying its because homeonwers never marked the jobs as completed on their app or whatever. Even right now, we have done thousands of dollars this week, worth of work for the lead company yet havent been paid any of it. What is my option to enforce payment, and basically let them know we do not play around when it comes to non payment. They get leads from HomeAdvisor as well. Many times we have been stiffed through them even out of our estimate costs. We charge a 100-150$ fee to even come out to the home or property, as it weeds out price shoppers and tire kickers. Yet the homeowner just cancels the job and claim nobody ever showed up. Ive got gps trackers on all our company cars and know when people show up to addresses. Would an attorney who knows about the suits against Handy Technologies, be able to help me? They are a good stream of constant service call work, but their payment issues arent good. If someone can help, it would be appreciated. Yall are more than welcome to email me at info@bhrconstructionco.com I really want to get this bs resolved. I dont work for our clients for free, but Handy Technologies has screwed us out of so much money.