Fatal error: Uncaught Error: Call to undefined method Mage_Catalog_Model_Product_Type_Simple::getUsedProducts() in /var/www/html/app/code/local/Webkul/Preorder/controllers/IndexController.php:8 Stack trace: #0 /var/www/html/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Webkul_Preorder_IndexController->indexAction() #1 /var/www/html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('index') #2 /var/www/html/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http)) #3 /var/www/html/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch() #4 /var/www/html/app/Mage.php(683): Mage_Core_Model_App->run(Array) #5 /var/www/html/index.php(83): Mage::run('', 'store') #6 {main} thrown in /var/www/html/app/code/local/Webkul/Preorder/controllers/IndexController.php on line 8