Problem running mysql query with XPDO

SELECT COUNT( * ) AS  `Rows` , diallednumber
FROM logData
GROUP BY diallednumber
ORDER BY  `Rows` DESC 
LIMIT 20

        //Query to find most common dialled numbers
        $c = $modx->myDB->newQuery('LogData');
	$c->select('COUNT( * ) AS  `Rows` , diallednumber');
	$c->groupby('diallednumber');
	$c->sortby('Rows', 'DESC');
	$c->limit(1);

        //Total found results
        $total = $modx->myDB->getCount('LogData', $c);
        echo '<p>Total records found: ' . $total . '</p>';

        //Run query
	$results = $modx->myDB->getCollection('LogData', $c);

$results = $modx->myDB->getCollection('LogData', $c);

$stmt = $c->prepare();
if ($stmt && $stmt->execute()) {
    $results = $stmt->fetchAll(PDO::FETCH_ASSOC);
} else {
    /* there was an error, handle it */
}

$total = $modx->myDB->getCount('LogData', $c);
echo '<p>Total records found: ' . $total . '</p>';