Do I need a visa?

I'm a Korean(official passport holder) who is a representative of a Korean public company and plan to visit Shanghai soon. I visited Chinese Visa Application Service Center in Toranomon last week to get a visa and a staff member there explained to me that I should go to Consular Office of Chinese Embassy in Azabu. So I went there, but a female staff member told me that I need an invitation letter from an institution in China and a note verbal issued by Korean Embassy. In order to receive the note verbal, I contacted a person working for Korean Embassy in Tokyo and he told me that as far as he knows I don't need a visa, adding that Korean diplomatic, service or official passport holders are exempt from a visa to Mainland China for not more than 30 days. I would highly appreciate it if you kindly let me know which information is correct as soon as posssible. Thanks in advance!