/**

 Remove all possible fields

 **/

function mrj_remove_checkout_fields( $fields ) {

    // Billing fields

    unset( $fields['billing']['billing_state'] );

	unset( $fields['billing']['billing_company'] );

    // Shipping fields

    unset( $fields['shipping']['shipping_state'] );

	unset( $fields['shipping']['shipping_company'] );

    return $fields;

}

add_filter( 'woocommerce_checkout_fields', 'mrj_remove_checkout_fields' );