Data: Centers for Medicare & Medicaid Services; Note: Includes initiating parties or their representatives. For emergency and non-emergency services; Chart: Madison Dong/Axios Visuals Insurers and providers are overwhelming an arbitration system Congress set up to resolve billing disputes as part of the law to prevent surprise medical bills, according to CMS data. Why it matters: The No Surprises Act, which went into effect earlier this year, protected privately insured patients from getting stuck holding the bag when there’s a disagreement over the cost of out-of-network care. But the mechanism for deciding who ultimately pays — which allows providers to appeal out-of-network payments they find unreasonable with a third-party arbitrator —…