Non B-Immigrant Visa Cancellation

Hi, 

Currently I hold a multiple entry Non-B Immigrant Visa valid till mid of November. I also hold a valid Work Permit valid till March 2013. my Current job is completed and have got a new job. But current employer is not ready to cancel the Visa. I went down to labor office today and understood I could cancel the work permit myself. Do anyone have idea if I could cancel the Non-Immigrant visa without my current employer or his authorized person and what all documents are needed to cancel the Non B-Immigrant visa. My new employer is ready to apply for new Non B-Immigrant visa and with necessary documents. Please advice...

Thanks
TestVisa