fatal error after the last update

adding a product to the basket will trigger a fatal error. the error log:

Stack trace:
#0 /home/websitename/public_html/wp-content/plugins/samedaycourier-shipping/samedaycourier-shipping.php(236): SamedayCourierHelperClass::isTesting()
#1 /home/websitename/public_html/wp-content/plugins/samedaycourier-shipping/samedaycourier-shipping.php(90): SamedayCourier_Shipping_Method->getAvailableServices()
#2 /home/websitename/public_html/wp-content/plugins/woocommerce/includes/abstracts/abstract-wc-shipping-method.php(233): SamedayCourier_Shipping_Method->calculate_shipping(Array)
#3 /home/websitename/public_html/wp-content/plugins/woocommerce/includes/class-wc-shipping.php(348): WC_Shipping_Method->get_rates_for_package(Array)
#4 /home/websitename/public_html/wp-content/plugins/woocommerce/includes/class-wc-shipping.php(260): WC_Shipping->calculate_shipping_for_package(A in /home/websitename/public_html/wp-content/plugins/samedaycourier-shipping/classes/samedaycourier-helper-class.php on line 39