username() function with Azure AD

Hi,

 I am using function username() to filter data for users in my organisation so that they don't have to filter reports by name to see their data. 

I have this problem, moste users get as result of function username() their email and some users  get AD username like AD/name.lastname , then this filters isn not working. 

How can I check or change this username source that function usrename() gets result ?