Can't change dynamic text field with AS3

programming flash
1

I have my movie linked to an external AS3 file with this:

package com {
 
 import flash.display.MovieClip;
 import flash.display.Stage;
 import com.lobby;
 
 public class game extends MovieClip {
  
  public function game():void {
   
  }
 }
}

then in my lobby class file I have:

package com {
 
 import flash.display.MovieClip;
 import flash.display.Stage;
 
 public class lobby extends MovieClip {
  
  public function lobby():void {
   server_time.text = 'test';
  }
 }
}

however it gives me that server_time doesn’t exist. I have tried root and parent… what am I doing wrong? Please help me understand the levels here.