Can a company rescind job offers.

I am an International student. I applied for an internship at Andersen Tax and got accepted. I was supposed to in February and needed to meet with my director Manager before because she wanted to get to know me. After our meeting, she offer me a full-time job after my internship because I told her that I was offered a full-time job with another company and she wanted to bit their offer. So, after I received their offer, I wanted to discuss some terms such as sponsorship because my other company was offering me that. So, I emailed the operations & Human Resources Manager regarding the questions. The Operations & Human Resources Manager said that the company does not sponsor and now he wants to rescind both offers; The internship which I already sign and the full-time one.

Can they do it and what should I do? Should I contact the Managing Director who offers me that full-time position? I need help because I need this internship for my signature experience as a senior in accounting.

Thank you