Change currency symbol

Hi,

The currency symbol filter was worked perfectly, but seems not any more.
As it mentioned on this page: https://wordpress.org/support/topic/change-the-currency-symbol-from-to-usd-in-woocommerce/, this code
add_filter( ‘woocommerce_currency_symbols’, ‘change_currency_symbol’ );
function change_currency_symbol( $symbols ) {
$symbols[‘USD’] = ‘USD $’;
return $symbols;
}
do nothing.
Do you have any other idea, how can I change the currency symbol?

Thank you in advance,

Sziban