If that is the case, be careful.

Remember, if there is a GAP between your F1 and H1, your status change to H1 can not be approved. You have to leave and come back on H1 visa after your H1B (employer part)is approved. Premium process may help you avoid the problem. But the strgegy may fail if officer find out that you does not complete your PHD study . The best way is to extend your F1 and send CIS a copy of your I-20.