<?php

$arr = array (
  '0'=> array (
    'L_TRANSACTIONID0'=> "62M97388AY676841D"
  ),
  '1'=> array (
    'L_TRANSACTIONID1'=> "9FF44950UY3240528"
  ),
  '2'=> array (
    'L_STATUS0'=> "Completed"
  ),
  '3'=> array (
    'L_STATUS1'=> "Completed"
  ),
);

$labels = array('L_TRANSACTIONID', 'L_STATUS');
$res = array();
foreach($arr as $val) {
  $key = str_replace($labels, '', key($val));
  $res[$key] = isset($res[$key]) ? array_merge($res[$key], $val) : $val;
}

print_r($res);

Array
(
    [0] => Array
        (
            [L_TRANSACTIONID0] => 62M97388AY676841D
            [L_STATUS0] => Completed
        )

    [1] => Array
        (
            [L_TRANSACTIONID1] => 9FF44950UY3240528
            [L_STATUS1] => Completed
        )

)