Mute button Screw is stuck. Help

Hey Guys!

So I was just replacing my iPhone 6s Housing, but when I got to Step 52 in the Replacement Guide I came across the Muteswitch Screw. I tried for a Long time to get it out with the Phillips #000 (the one used in the Guide) but didn't get it out. Now the head is round and I still can't get it out. Hope someone can help me :)

Thanks Mark!