Applying for Z visa, when already have a valid stident visa

hello.I recently got my X2 visa for phd stidies in China,.and just after getting my visa i got my work permit from company . I made.a.mistake that i applied for study visa in hurry. Now my question is,.this visa is valid for three month, but if i do not to university, they will cancel my admission. To apply for a Z visa, the counseler said i need an N.O.C, but the university will not issue N.O.C as i am not going to register there, and i am not even their student if i do not register. What is the solution, as i want to go on Z visa, not on sudy visa..