I was named Bien but people ussuall call me Thuy/ I ussuall is called Thuy

I think, there is a little bit different.And  "named" as I was explained once, It is rather literal than formal. 

I dont know it for sure. In my opinion, 

"is named" is the name which A give it to B. Ex: Child was named by his father. 

"is called" is everybody call the name of someone.