During Open Enrollment, you can shop for a different plan. If your insurance company won’t offer any other Marketplace plans next year, you should sign up for new coverage during Open Enrollment in order to remain insured next year and receive the most accurate premium tax credit possible. If you don’t act by the end of Open Enrollment and you live in a HealthCare.gov state, the Marketplace will automatically enroll you in a new plan offered by a different insurance company. The Marketplace will try to pick the lowest cost plan that is as similar as possible to the one you have now.
If your insurance company is discontinuing your plan but will continue to offer other plans, and if you live in a HealthCare.gov state, your choices are similar: you can shop for a new plan during Open Enrollment, or you can do nothing and your insurance company will automatically enroll you in the lowest cost plan it offers for next year that is similar to what you had this year. The notice you received from your insurer should describe that alternative plan and how it differs from your current plan.