woocommerce_checkout_fields_remove

woocommerce_checkout_fields.php

<?php
add_filter( 'woocommerce_checkout_fields', function( $fields ) {

    // Remove fields
    unset( $fields['billing']['billing_last_name'] );
    unset( $fields['billing']['billing_company'] );
    unset( $fields['billing']['billing_country'] );
    unset( $fields['billing']['billing_address_2'] );
    unset( $fields['billing']['billing_city'] );
    unset( $fields['billing']['billing_postcode'] );
    unset( $fields['billing']['billing_email'] );
    unset( $fields['shipping'] );

    // Make phone required
    $fields['billing']['billing_phone']['required'] = true;
    $fields['billing']['billing_phone']['label'] = 'Phone';

    return $fields;
});

add_filter( 'woocommerce_checkout_fields', function( $fields ) {

    $fields['billing']['billing_state']['default'] = 'TZ02';

    return $fields;
});

add_action( 'woocommerce_before_checkout_form', function() {

    if ( WC()->customer && empty( WC()->customer->get_billing_state() ) ) {
        WC()->customer->set_billing_state( 'TZ02' );
    }

});