How can i unscrew the bottom screw of my zippo lighter?

i need to replace the flint of my zippo, but the thing is i cant unscrew the bottom screw. i already used different kinds of screwdrivers but it does not unscrew. is it broken? if it is ,where can i repair this in the philippines?|||You need to be standing on your head to do this. Other wise the lighter would be upside down and the safety feature will prevent the removal of the screw.|||send it to zippo at Bradford,pa|||Use the edge of a dime. If that does not work, send it back to Zippo and they will fix it free and send ti back to you