在管理部分列中对基本ACF进行排序

I'm trying to sort my columns alphabetically, but when I use the pre_get_posts() function it breaks the site. I imagine this is because the ACF I'm using is just a 2 letter text field and I don't know how to reference that in the function

    function get_geoCode($post_ID) {
    $geoCode = the_field('geo_code');
    if ($geoCode) {
        return $geoCode;
   }
}
function geo_row($defaults) {
    $defaults['geo_col'] = 'Geo Code';
    return $defaults;
}

function geo_row_content($column_name, $post_ID) {
    if ($column_name == 'geo_col') {
        $geo_code_id = get_geoCode($post_ID);
        if ($geo_code_id) {
            echo  $geo_code_id;
         }
     }
}


// CALL THE ABOVE FUNCTIONS +  FILTERS
add_filter('manage_page_posts_columns', 'geo_row', 10);
 add_filter('manage_edit-page_sortable_columns', 'geo_columns');

function geo_columns( $columns ) {
   $columns['geo_col'] = 'Geo Code';

   //To make a column 'un-sortable' remove it from the array
    //unset($columns['date']);

    return $columns;
}

add_action('manage_page_posts_custom_column', 'geo_row_content', 10, 2);

 add_action( 'pre_get_posts', 'geoCol_orderby' );
function geoCol_orderby( $query ) {
    if( ! is_admin() )
          return;

    $orderby = $query->get( 'orderby');

    if( 'Geo Code' == $orderby ) {
        $query->set('meta_key','geo_col');
        $query->set('orderby','meta_value_num');
    }
}

So the column shows with the ACF text value but it sorts by something that isn't alphabetical. If I enable the pre_get_posts function it breaks the site.

Any idea how to get an alphabetical value from an ACF text field?