F2-F1-H1B

I entered the U.S. originally on an F-2 visa in 4/2001. I then changed my visa to F-1 after I got admitted to graduate school 5/2002. I think I should be eligible for the $5,000 tax exemption based on Article 20 of the U.S./China treaty, but my payroll department said in order to be qualified for the exemption, I must have entered the U.S. on an F-1 visa the first time. Is that correct?

Thanks in advance!!!!!!!!!!1