Recent legal settlements with big health insurers may allow some managed-care plan participants to begin recovering some of the money they may have overpaid for using out-of-network doctors and hospitals. So far, insurers UnitedHealth Group Inc., Aetna Inc., and Health Net Inc. have agreed to make millions of dollars in funds available to patients and, in some cases, physicians for possibly having shortchanged them in the past. A number of other legal actions are pending that seek redress for patients and healthcare providers who claim they were underpaid by insurers for out-of-network services.