The file permission is okay (0777) but i think your on the shared server, so to delete your file correctly use; 1. create a correct path to your file
// delete from folder
$filename = 'test.txt';
$ifile = '/newy/made/link/uploads/'. $filename; // this is the actual path to the file you want to delete.
unlink($_SERVER['DOCUMENT_ROOT'] .$ifile); // use server document root
// your file will be removed from the folder
That small code will do the magic and remove any selected file you want from any folder provided the actual file path is collect.