Please help!!My I-94 is expiring

the officer only granted me to stay till Jun. this year since I haven't had my passport extended when I came back from China last Oct. Now I am trying to file extension on I94 but don't know which form I should use. I can't even get a live person to make an appointment to go the local Immigration office! USIC's serive really sucks! PLEASE HELP!! Do I just mail out the form?(which form) and do I need to pay for taht?

Thank you thank you!!!