functions.php

add_filter('woocommerce_currency_symbol', 'techbear_change_multiple_currencies_symbols', 10, 2);
function techbear_change_multiple_currencies_symbols( $currency_symbol, $currency ) {
    switch( $currency ) {
        case 'RUB': $currency_symbol = 'руб.'; break;
        case 'BYN': $currency_symbol = 'бел. руб.'; break;
        case 'KZT': $currency_symbol = 'тнг.'; break;
    }
    return $currency_symbol;
}