There is no downgrade option at the moment. You will have to cancel your current plan at the end of the month and then can reapply for the desired plan. Please note that refunds will not be eligible for downgrades if the account has already been used. All previous projects and voices will stay intact.
If you have bought your plan in the last 24 hours and not started using your account yet, you can write to us with a downgrade request at firstname.lastname@example.org