WOOCS - WooCommerce Currency Switcher

Formidable Forms – Form Builder for WordPress

Plugin link: https://wordpress.org/plugins/formidable/

In file \wp-content\plugins\formidable-woocommerce\assets\scripts\formidable-addons.js -> function wc_fp_update_totals() insert next code:

if (woocs_current_currency != undefined && woocs_current_currency['rate'] != undefined && calc_value != undefined) {
    calc_value = calc_value * woocs_current_currency['rate'];
}