Final answer:
If a service is not listed in the Medicare EOC or approved by the plan, neither Medicare nor the plan will cover the service, making the beneficiary liable for the costs.
Step-by-step explanation:
If a service isn't listed in the Explanation of Coverage (EOC) or approved by the plan, Medicare and the plan will most likely not cover the service. This means that if a beneficiary receives a service that is neither listed in the EOC nor pre-approved by their Medicare Advantage or other Medicare plan, they could be responsible for the full cost of that service. Medicare plans have specific rules outlining which services are covered and which are not, and these are detailed in the EOC document that beneficiaries receive.