You can deactivate your user account by clicking on your photo on the top right corner of the web app's screen and then select Edit Profile. At the bottom of your profile page, select Deactivate my Account.
A pop up message will appear on your screen. Press Confirm to complete the deactivation.
Note: You can always deactivate your account. However, if you're the only administrator, you need to add another administrator first. Otherwise, you must deactivate the contact list of your organization. To do it, follow the steps below.
From the main menu press Settings and then in the submenu select Edit Company
At the bottom of the page, select Deactivate Address Book
A pop up message will appear on your screen. Select Confirm to complete the deactivation.
Note: When you deactivate an address book, all the user accounts which are connected with this address book will automatically be deactivated.