It always pays off to review your current insurance package each year and decide if the plan is right for your specific needs. Each year you can review your coverage during Open Enrollment and make changes to your plan.
You can change your Original Medicare which are Parts A and B to a Private Medicare Advantage Plan which is a Part C plan. Or you can change from Part C back to Original Medicare. This is the time you can switch a Part D prescription drug plan, maybe join or drop it. Medicare Advantage Plans can be switched.
Speaking with a qualified insurance agent is beneficial in that they can help find the best combination of plans to best fit your personal needs.