show different shipping label

thanks for your great plugin.

We are using your plugin since a few years and all worked perfectly.

We have the shipping label as “Envio” where the plugin adds the shipping price…

the rare thing we need is that, when the price is 0 ( because between 14 and 19 Kg the shipping is free) …. the label showed should be like “Envio 0€” or a custom label like “ENVIO GRATIS”…

Is there a way to have that behaviour?

Thank you very much

The page I need help with: [log in to see the link]