I have applied Residence Permit in Wroclaw region as Volunteer and now, I want to apply a student permit since I get accepted to one of the university in Poznan to study full-time?

If the application for temporary residence permit  in Wrocław is still in proces you should send to Wrocław (The Office of Dolnośląski Province) the information of changing the place of stay and purpose; Application from Wrocław should be transfered to Poznan (The Office of Wielkopolska Province).