Restrict content based on buy woocommerce product and payment method

Hi Dear
I’m using woocommerce an I encounter by a problem but unfortunately nobody answer to me
the problem is:
I did solution for restriction content on page: Restrict content based on buy woocommerce product
But This snippet won’t restrict content buy payment method if somebody purchase the goods by “Cash On Delivery” way , the hidden items will be appear whereas this is not secure way because in this scenario in woocommerce order page the order is not complete . 
how can I improve this code?
your sincerily