Saving a data to two different nodes with same node id?
As Paul commented, there is already a system to keep track of changes. You can enable node revisioning through the UI by going to Config > Structure > Content types > [Content Type] > Edit and select the Create new revision option under Publishing options. Now every on-site node edit will be registered as a revision and the previous values are logged in the Revisions tab (next to edit).

If you need to programmatically create a new revision, you can do it as follows:

$node = node_load($nid);

$node-&gt;field_call_response['und'][0]['tid'] = $call_response;

$node-&gt;revision = 1; // Save new revision
$node-&gt;log = "Explain what you changed";
node_save($node);