// Add phone # fields
add_filter( 'woocommerce_checkout_fields' , 'custom_override_checkout_fields' );
function custom_override_checkout_fields( $fields ) {
    $fields['billing']['cell_phone'] = array(
    'label'     => __('Cell Phone', 'woocommerce'),
    'placeholder'   => _x('', 'placeholder', 'woocommerce'),
    'required'  => false,
    'class'     => array('form-row-first'),
    'clear'     => false
     );
    $fields['billing']['biz_phone'] = array(
    'label'     => __('Business Phone', 'woocommerce'),
    'placeholder'   => _x('', 'placeholder', 'woocommerce'),
    'required'  => false,
    'class'     => array('form-row-last'),
    'clear'     => true
     );
     return $fields;
}

// Update the order meta with field value for cell phone
add_action( 'woocommerce_checkout_update_order_meta', 'cell_phone_field_update_order_meta' );
function cell_phone_field_update_order_meta( $order_id ) {
    if ( ! empty( $_POST['cell_phone'] ) ) {
        update_post_meta( $order_id, 'Cell Phone', sanitize_text_field( $_POST['cell_phone'] ) );
    }
}

// Update the order meta with field value for biz phone
add_action( 'woocommerce_checkout_update_order_meta', 'biz_phone_field_update_order_meta' );
function biz_phone_field_update_order_meta( $order_id ) {
    if ( ! empty( $_POST['biz_phone'] ) ) {
        update_post_meta( $order_id, 'Business Phone', sanitize_text_field( $_POST['biz_phone'] ) );
    }
}

// Display cell phone # on the order edit page
add_action( 'woocommerce_admin_order_data_after_billing_address', 'cell_phone_field_display_admin_order_meta', 10, 1 );
function cell_phone_field_display_admin_order_meta($order){
    echo '<p><strong>'.__('Cell Phone').':</strong> ' . get_post_meta( $order->id, 'Cell Phone', true ) . '</p>';
}

// Display biz phone # on the order edit page
add_action( 'woocommerce_admin_order_data_after_billing_address', 'biz_phone_field_display_admin_order_meta', 10, 1 );
function biz_phone_field_display_admin_order_meta($order){
    echo '<p><strong>'.__('Business Phone').':</strong> ' . get_post_meta( $order->id, 'Business Phone', true ) . '</p>';
}