I dont want the contacts list to load automatically when I enter any letter after hitting 'TO' button

I dont want the contacts list to load automatically when I enter any letter after hitting 'TO' button

I dont want the contacts list to load automatically when I enter any letter after hitting 'TO' button as this is my business email id's and I dont want my employees to know the email ids of the higher officials. I dont want to load the list as shown in the image.