You need to change the task status available for your users to pick
To change the available status' in tasks
- Log in to Zoho CRM with Administrator privileges.
- Go to Setup > Customization > Modules and Fields
- Click the Task module from the Modules list view.
- Click on the Tasks Module
- Select the layout you want to modify (standard)
- Click on the Ellipse (...) next to Status
- Select Edit Properties
- Change the pick list options