My working Visa extension in China

I am an Afghan living in Beijing. It's been almost four years I am working and living in Beijing. from 2009 to Sept 2011, I worked in the embassy of Afghanistan in Beijing holding service passport but after then I quit my job and started to get enrolled in one of the universities here in Beijing. I have currently the student one year multiple entry visa. the visa validity is upto Sept 29, 2012. Since I am living and working in Beijing, I would like to extend my visa. Therefore, I seek your assistance and guidance in this regards. For your information, I am teaching English in one of the well-known Institutions as well.
Look forward to hearing back from you.
Regards,
Feroz