You don't need to cancel your old Medicare drug plan. Your old Medicare drug plan coverage will end when your new drug plan begins.
If you want to join a plan or switch plans, do so as soon as possible so you’ll have your membership card when your coverage begins, and you can get your prescriptions filled without delay. You should get a letter from your new Medicare drug plan telling you when your coverage begins.
Don't give personal information to plans that call you unless you're already a member of the plan.