Method TBS->Show()
does not return the binary result of the merge.
According to the manual, you have to do this in order to retrieve the binary content:
$TBS->Show(OPENTBS_STRING);
$string = $TBS->Source;
So your code could be like this:
$TBS->Show(OPENTBS_STRING);
->setSubject('Customer General Email from '. $date->format("m-d-Y H:i"))
->setFrom('avangardauto33@gmail.com')
->attach(
\Swift_Attachment::newInstance()
->setFilename('space_calculator_results.odt')
->setContentType('application/odt')
->setBody($TBS->Source)
)
->setBody($this->renderView(
'WinslowUserBundle:User:calc_results_email.html.twig',
array('data' => $data)), 'text/html');
$this->get('mailer')->send($message);