Undefined index when trying to get result from JSON to array

I received error when trying to call single array from json_decode()

Undefined Index AccontNumber

And I have try to use Isset to the variable and doesnt get any result, Where do I doing wrong ?

    $this->getToken();
    $path = '/banking/v2/corporates/BCAAPI2016/accounts/0201245680/statements?StartDate=2016-09-01&EndDate=2016-09-01';
    $method = 'GET';
    $data = array();
    $this->getSignature($path, $method, $data);
    $headers = array(
      'X-BCA-Key: '.self::$api_key,
      'X-BCA-Timestamp: '.self::$timestamp,
      'Authorization: Bearer '.self::$access_token,
      'X-BCA-Signature: '.self::$signature,
      'Content-Type: application/json',
      'Origin: '.$_SERVER['SERVER_NAME']
      );
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, self::$main_url.$path);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt_array($ch, array(
        CURLOPT_RETURNTRANSFER => TRUE,
        CURLOPT_HTTPHEADER => $headers,
        ));
    $output = curl_exec($ch); // This is API Response
    curl_close($ch);
//this part I get error
    $result = json_decode($output,true);

    return view("bca.bca", [
        "result" => $result
        ]);

my view

@if ($result['AccountDetailDataSuccess'])







@elseif ($result['AccountDetailDataFailed'])



@endif

and this the result if I var_dump($result)

array(2) { ["AccountDetailDataSuccess"]=> array(1) { [0]=> array(7) { ["AccountNumber"]=> string(10) "0201245680" ["Currency"]=> string(3) "IDR" ["Balance"]=> string(12) "118849999.53" ["AvailableBalance"]=> string(12) "118849999.53" ["FloatAmount"]=> string(4) "0.00" ["HoldAmount"]=> string(4) "0.00" ["Plafon"]=> string(4) "0.00" } } ["AccountDetailDataFailed"]=> array(0) { } }

How can I call just one single array from the JSON result ?

via Chebli Mohamed