I'm in college and I've already passed my Level 3 exams, I want to pick up ...?

... documents, but they tell me that if I do this, they will not give me a certificate of studying at this college and obtaining a 3rd grade, they also say that they will not give me the opportunity to work in practice, but only in their institutions and without any remuneration , I study on a paid basis. I am 19 years old. Should they issue me this certificate and is the practice situation legal?