microsoft office - Font in Word changes as soon the user types

When I open a new, blank document in MS Word 2016 the font Calibri is selected. The style template is default which shows Calibri when right click => modify on it. (http://www.pcworld.com/article/2098430/how-to-set-and-keep-your-preferred-default-font-in-word.html)

However when I start typing the font changes to Times New Roman. How can I change this behaviour? Word and Outlook are affected, Powerpoint and Excel not.