Change taxonomy term field into text field in content-type
Eventually, I simply used a PHP script I execute in mysite/devel/php to copy my taxonomy term field value to my new text field:

$nodes = node_load_multiple(array(), array('type' =&gt; 'contact'));
foreach($nodes as $node) {
  if ($node != NULL) {
    $tid = $node-&gt;field_title['und'][0]['tid'];
    $term = taxonomy_term_load($tid);
    $name = $term-&gt;name;
    $node-&gt;field_function_title['und'][0]['value'] = $name;
    $node = node_submit($node);
    node_save($node);
  }
}