Wrong (Z) category, looking for an option to change it to F-type

Hi, I am currently on a Z category in Shanghai. Unfortunately this is the wrong type for me since I'm doing a 3-month unpaid internship. I have visited the PSB exit-entry bureau to explain my situation. They have confirmed that my visa is indeed the wrong type. However, they were less than willing to explain what I should do next. Does anybody have any advice over options to resolve this problem or whether it is possible to change from category Z to F?

Thanks!
Ps: I should mention that all the previous interns for my company were issued an F type