How do I terminate my Medicare Part B (medical insurance)?
"You can voluntarily terminate your Medicare Part B (medical insurance). However, since this is a serious decision, you will need to have a personal interview with a Social Security representative first. The representative will help you complete Form CMS 1763. This form is not available online. To schedule your interview, call us at 1-800-772-1213 (TTY: 1-800-325-0778) Monday through Friday from 7:00 AM to 7:00 PM, or contact your nearest Social Security office." https://faq.ssa.gov/link/portal/34011/34019/Article/4074/How-do-I-terminate-my-Medicare-Part-B-medical-insurance