I'm a student and I applied 6 months visa F for my practical internship in Shanghai under Company A but after a month of internship, I have another offer from company B which I love and suit to my field better. So the question is, if I'm leaving this company A and go to B, will it be illegal as I am now using the company A invitation letter, what should I do if I really wanted to join in company B for internship, I do not want to miss this opportunity. Thanks guys