Change Checkout Address Label

functions.php

<?php

// method 1.
add_filter( 'woocommerce_checkout_fields', function( $fields ) {
  $fields['billing']['billing_state']['label']      = 'Provinsi';
  $fields['billing']['billing_city']['label']       = 'Kabupaten';
  $fields['billing']['billing_district']['label']   = 'Kecamatan';
  $fields['shipping']['shipping_state']['label']    = 'Provinsi';
  $fields['shipping']['shipping_city']['label']     = 'Kabupaten';
  $fields['shipping']['shipping_district']['label'] = 'Kecamatan';
  return $fields;
}, 99 );

// method 2.
add_filter( 'woocommerce_billing_fields', function( $fields ) {
  $fields['billing_state']['label']    = 'Provinsi';
  $fields['billing_city']['label']     = 'Kabupaten';
  $fields['billing_district']['label'] = 'Kecamatan';
  return $fields;
}, 99 );
add_filter( 'woocommerce_shipping_fields', function( $fields ) {
  $fields['shipping_state']['label']    = 'Provinsi';
  $fields['shipping_city']['label']     = 'Kabupaten';
  $fields['shipping_district']['label'] = 'Kecamatan';
  return $fields;
}, 99 );

// method 3.
add_filter( 'woocommerce_get_country_locale', function( $fields ) {
  $fields['ID']['state']['label'] = 'Provinsi';
  $fields['ID']['city']['label']  = 'Kabupaten';
  return $fields;
}, 99 );