Interfer with plugin

Hello im tryin to show not only the symbol currency but USD, EUR etc too, i try a code but it doesnt work if this plugin is activated.
Any tips?

add_filter(‘woocommerce_currency_symbol’, ‘change_existing_currency_symbol’, 10, 2);

function change_existing_currency_symbol( $currency_symbol, $currency ) {
switch( $currency ) {
case ‘EUR’: $currency_symbol = ‘Eur ‘; break;
case ‘USD’: $currency_symbol = ‘Dollars ‘; break;
case ‘MXN’: $currency_symbol = ‘Pesos $’; break;
}
return $currency_symbol;
}