[Dont use this plugin] use Woocommerce Pay for Payment

Thanks for author of the plugin. But this plugin is outdated and it hats way more features and actually does not totally work as advertised.

Solution use this: Woocommerce Pay for Payment

Use Woocommerce Pay for Payment it has way more features. And will solve all the problems you have with this plugin.

https://wordpress.org/plugins/woocommerce-add-extra-charges-option-to-payment-gateways/