ERROR!!!

Hey,

I get this error when trying to make payment via the beanstream plugin:

Fatal error: Call to undefined method WooCommerce::add_error() in /home/content/p3pnexwpnas06_data01/27/2464527/html/wp-content/plugins/woocommerce-beanstream-payment-gateway/woocommerce-gateway-beanstream.php on line 345

CAN YOU PLEASE HELP ME FIX THIS!!!!

http://www.orgo.ca

https://ww.wp.xz.cn/plugins/woocommerce-beanstream-payment-gateway/