class Kol_PaymentToggle_Model_Observer
{
    public function paymentMethodIsActive(Varien_Event_Observer $observer) {
        $event  = $observer->getEvent();
        $method = $event->getMethodInstance();
        $result = $event->getResult();
        $quote = $observer->getEvent()->getQuote();
        $shippingMethod = $quote->getShippingAddress()->getShippingMethod();
        if($shippingMethod == "standardshipping" || $shippingMethod == "free") {
            if($method->getCode() == 'cashondelivery' ) {
                $result->isAvailable = false;
            }
        }
    }
}