Assigning the operator role while adding an operator is the pre-requisite for this configuration.
The administrator is given the priviledge to add team members, especially configuring them into one of the roles.
The main aim is to allocate the right role to each sales representative. The administrator has the power to change the role of the sales representatives at any point of time.
So go to your Operators tab under Settings, select the operator you wish to change the role of. Select the required role. Click Update
To learn more about changing operator role, Click here