$this->db->where('lower(status) <>', 'completed');
$this->db->order_by('calldate','asc');

$q1 = $this->db->get('records'); //where and orderby applies to this query only
$q2 = $this->db->get('other_records'); //where and orderby does not apply to this
$data1 = $q1->result_array();
$data2 = $q2->result_array();
$data = array_merge($data1, $data2);

$this->db->where('lower(status) <>', 'completed');
        $this->db->order_by('calldate','asc');

        $q = $this->db->get('records'); //where and orderby applies to this query only
        $data1 = $q->result_array();
        $q = $this->db->get('other_records'); //where and orderby does not apply to this

        $data2 = $q->result_array();
        $data = array_merge($data1, $data2);

SELECT * FROM records WHERE lower(status)<>'completed' ORDER BY calldate ASC
UNION
SELECT * FROM other_records WHERE lower(status)<>'completed' ORDER BY calldate ASC