File I-539 immediately. See the following websites for more information.
https://www.wsuoiss.wayne.edu/sections/immigration_info/b1_b2_and_wb_wt_status/b1_b2_extension
http://www.uscis.gov/portal/site/uscis/menuitem.5af9bb95919f35e66f614176543f6d1a/?vgnextoid=94d12c1a6855d010VgnVCM10000048f3d6a1RCRD&vgnextchannel=db029c7755cb9010VgnVCM10000045f3d6a1RCRD
https://www.wsuoiss.wayne.edu/sections/immigration_info/b1_b2_and_wb_wt_status/b1_b2_extension
http://www.uscis.gov/portal/site/uscis/menuitem.5af9bb95919f35e66f614176543f6d1a/?vgnextoid=94d12c1a6855d010VgnVCM10000048f3d6a1RCRD&vgnextchannel=db029c7755cb9010VgnVCM10000045f3d6a1RCRD