If you downgrade from Business plan to Starter plan you will still be on the business plan until the end of your billing cycle but you must remove all users in your organization because starter plan is only available for a single user.

 After the billing cycle ends you will:

 - Lose access to your teams and shared documents among them.

 - Cannot use SMS or Absher Verification anymore.

 - Cannot add any users or send documents in bulk.

 - Cannot use custom branding.