My F visa expiring at the end of July. My internship terminated prematurely, how to renew my Business Visa (F visa)?

In Shanghai.

While renewing my F visa through my host college, they said I need a letter from the company I am interning with.

The company has prematurely ended my internship contract, for the end of this month, when the contract itself is for next April. I need a letter from saying I'm working in August, but they say they won't give me that letter.

Without that letter, my college say they won't give me a document to give to the Entry Exit bureau.

I want to stay in the country to catch the flight I booked for the end of August, but my F visa will expire at the end of July unless I can renew it by some means.

I am obviously frustrated that the contract had its terms altered with only 2 weeks notice.
What remedies can you suggest? Either appealing to the company/college to give a letter or somehow converting my F visa to an L visa.