$matches = array();
if (is_array ($users) && count ($users) > 0) {
  foreach ($users as $user) {
    $user = new WP_User ($user->ID);
    $matches[] = "'" . get_user_field("cell_no", $user->ID) . cellmap(get_user_field("cell_carrier",$user->ID)) . "'";
  }
}

Array
(
[0] => '1234567891@vtext.com'
[1] => '3216549871@vtext.com'
[2] => '9876543211@vtext.com'
[3] => '6543219877@vtext.com'
)

$cell_list = implode(", ", $matches);

$outgoing_message = Swift_Message::newInstance('')
  ->setFrom(array('no-reply@mydomain.com' => 'Mydomain'))
  ->setTo($cell_list)
  ->setBody($message);

// Send the message
$result = $mailer->send($outgoing_message);

$cell_list = implode(", ", $matches);
$outgoing_message = Swift_Message::newInstance('')
  ->setFrom(array('no-reply@mydomain.com' => 'Mydomain'))
  ->setTo($cell_list)
  ->setBody($message);

$outgoing_message = Swift_Message::newInstance('')
  ->setFrom(array('no-reply@mydomain.com' => 'Mydomain'))
  ->setTo($matches)
  ->setBody($message);