With major changes to anything there will always be a transition period. This transition period will last from April 2018 through December 2018. During this time all providers and insurance carriers will have time to update their records and their process for processing payments. I suggest keeping the old Medicare card in a safe place until after the transition.
https://www.cms.gov/Medicare/SSNRI/Index.html
New Medicare cards offer greater protection to more than 57.7 million Americans
Click the following link for the official press release from the Centers for Medicare and Medicaid Services
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