In order to make it even easier for those of you who use Zendesk Sell seasonally or for campaigns, we've introduced account deactivation. To deactivate your account, simply contact us here and request to have your account deactivated.
Once deactivated, no users on the account will be able to log in to Zendesk Sell (they will receive an email notification), either on the web or through the mobile apps. Following a deactivation, a user's API token will also be changed – this will disable any integrations they had enabled in Sell.
Naturally, since deactivated accounts are no longer active in Sell, you will not be billed while your account is deactivated. To reactivate your account again, simply log in again, and you will be prompted to select a plan to continue. You'll then be able to reactivate your users and continue using Zendesk Sell!
If you are looking to deactivate single user take a look here.