How do I file a formal complaint against Intuit Quickbooks?

For the past six months I have had several customers "dispute" their payments to our company after work has been done. According to Intuit Quickbooks information we should be receiving not only emails when a dispute is filed giving us the opportunity to file a rebuttal, which we are not receiving but also the most recent one never showed in the Resolution Center. The only way we even knew about it was when $7000 was withdrawn from our bank account. I have spent six months jumping through hoops with all of their "customer service" by sending in all of my documentation/proof that this is happening, I had my corporate IT team work to make sure that Intuit QB emails weren't being blocked or bounced back when sent to us, I have talked to our "rep" (useless), I have contacted the Office of the President (useless) and was even put in touch with "Risk Management Rep" in the disputes department......ALL OF WHICH have either passed the buck or said "SORRY there is nothing we can do". In the meantime, we have now LOST over $20,000 in work that we completed and have customers with free materials, equipment and labor. 

As much money as we pay into Intuit QB every single month/year not only for their program but for all of the "fees" for the merchant center this is an absolute DISGRACE! 

Other than filing a lawsuit against these customers, which we are doing, and filing a formal complaint with the Better Business Bureau which we will be doing, what other recourse is there?