From the National Council on Aging economic security blog, with good links:
You may have heard that, beginning this spring, Medicare will be sending out new cards [1] to all beneficiaries. The new card removes the current Social Security-based identifying number and replaces it with a random number/letter sequence that helps to reduce identity theft and fraud.
The Federal Trade Commission (FTC) warns against scammers posing as Medicare “agents” or health care providers telling seniors they need to purchase a replacement card. The new Medicare cards are free, and everyone with Medicare will be mailed a card between April 2018 – April 2019. The only action you need to take is to ensure Social Security has your current address,[2] as the new cards will be sent to the address in their files.
If you’ve been solicited by a possible Medicare scammer, report it by calling 1-800-HHS-TIPS (1-800-447-8477), or submit a complaint online[3] to the Office of the Inspector General of the U.S. Department of Health and Human Services.
Included at links:
[1] CMS.gov: how the new cards will look, “Learn how we’ll mail the new Medicare cards in phases by geographic location,” a video, an “Overview” section, “Quick Resources”, etc.
[2] A social security dot gov page of FAQs starting with “How can I change my address?” Links are in the answers.
[3] The “Report Fraud form” of the O.I.G. US Dept HHS.