Two of the most generous and popular Medicare supplement (Medigap) plans are getting phased out starting next year, but only to new beneficiaries. Beginning in 2020, plans F and C will no longer be available for those just joining Medicare. Plan F has been the top-selling Medigap plan for years, as it provides the broadest coverage of any of the Medigap plans. While premiums are relatively high, once you are enrolled you won't have to pay anything out of pocket for medical services covered under Medicare. What do Plan F and Plan C cover? The two soon-to-be discontinued plans both…