public function push($amount = null, $number = null, $reference = null, $command = null, $account = null)
    {
        $account = $account ?: $this->account;
        $configs = (new ConfigurationRepository)->useAccount($account);

        if (!$configs->getAccountKey('sandbox')) {
            throw new ErrorException('Cannot simulate a transaction in the live environment.');
        }

        $shortCode = $configs->getAccountKey('lnmo.shortcode');

        $body = [
            'CommandID'     => $command ?: $this->command,
            'Amount'        => $amount ?: $this->amount,
            'Msisdn'        => $number ?: $this->number,
            'ShortCode'     => $shortCode,
            'BillRefNumber' => $reference ?: $this->reference,
        ];

        try {
            $response = $this->makeRequest(
                $body,
                Core::instance()->getEndpoint(MPESA_SIMULATE, $account),
                $account
            );

            return json_decode($response->getBody());
        } catch (RequestException $exception) {
            return json_decode($exception->getResponse()->getBody());
        }
    }