UnitedHealthcare is suing a national dialysis company, claining American Renal Associates has been exploiting the insurance provider and its own poorer patients for money collected from dialysis treatment.

According to the New York Times, the company operates more than 200 clinics throughout the country and is partnered with the patient advocacy group the American Kidney Fund.

In the lawsuit filed July 1 in Florida, United alleged that American Renal Associates, using the American Kidney Funds’ influence, has fraudulently convinced patients to switch from their regular health coverage (such as cheap private plans or public plans like Medicaid) to the more expensive UnitedHealthCare, said the Times. The plan would help American Renal Associates make significantly more money—the Times points out that government plans often only reimburse up to $200 per dialysis treatment, while insurance providers like United might reimburse up to $4,000 per treatment.

United argues this scheme to get patients to switch is bad for them and for their customers—United has paid $2 million to American Renal Associates in 2016 so far (and saddled the insurer with more expensive, sicker patients who might otherwise be covered by government insurance), and patients are unwittingly being ushered into a private health plan with premiums they can’t actually afford. Some in the dialysis industry have pointed out the sketchy ethics of such a situation.

The vice president of American Renal Associates denied any wrongdoing in a statement to the Times, saying the company always puts patients first. But critics say the company mostly has its eye on the bottom line.