Go to your Client's section inside your account. (https://app.veryfi.com/clients/).
Click on the red trash can icon.
Confirm the deletion from your account. Please note that the client's account will not be deleted, just removed from your client's section.
Once a client has been removed from your billing, their subscription plan is changed to Starter. They will only have access to the free features and they will have to manually upgrade.
How to upgrade your Expense Management account