Mini Plugin: WooCommerce edit Free! Price String
This is a mini plugin that lets you edit the price string of WooCommerce products that are set free / zero price.
Since WooCommerce 3.0 there is no “Free!” text string used anymore. This plugin will install fine but might do nothing. I have not tested it with WooCommerce 3. Alternatively you can try this snippet
Download WooCommerce Change Free Price String plugin