Conversion of S typeto Student X type at PSB office

Hi, i am on dependent S type in Harbin, got Admission in a university and now want to change my visa from dependent to student. Is it posssible to change it st PSB Harbin?
Some old students are telling its not possible you have to go back and enter with X type again. SOme other suggests you have to exit again.
I am confused whether to apply or not for student X type as my family S type have still many months remaining and i cant afford to go now back as my classes is started.