In Japan it's totally OK to address friends or classmates by their family name, but between good friends or among people who they know each other well, it's not so common to call someone by family name(except for older people; it's basically considered as a bit rude to call older people/older friends by their first name).

And...  we seldom switch from calling first name to family name in any case, even if the relationship or friendship gets to be at outs like broken-up couples. :)