Can a visa be extended??

Hi good day..I'm currently holding a Z Chinese entry permit..and I should have until mar. 19 2017 to be able to go to china..
The thing is my oec clearance issued by Poea was not yet release..I am so concern that my Z type will about to expire..and I really have to go to china before mar. 19..if this happen is there any way I could ask for an extension for a visa while I'm still here in philippi es?..hope to hear from you soon..thank you.