Shipping method

I have installed “Advanced flat rate shipping for woocomerce” and have set two shipping method in it “Free shipping” – for rest of the categories and “Fixed charge shipping” for a specific category.

But when multiple products are selected from Free shipping collection and Fixed charge collection then at checkout customers are getting option to select from “Free Shipping” and “Fixed charge” shipping method, which should not be the case. If any product is selected from Fixed charge category then it should override the Free shipping method.

Please help