$insert_cmd = "INSERT INTO PhoneNumbers 
                 (cusID, adtID, pntID, phnPart1,       
                  phnPart2, phnPart3, phnExt)
               VALUES 
                  (?, ?, ?, ?, ?, ?, ?)";

$phone_insert = $gcssDBH->prepare($insert_cmd);

$phone_insert->bind_param(6,undef,SQL_VARCHAR); #bind undef -- execute will remember the bind type

$phone_insert->execute(
                        $row->{'cust_id'}, 
                        $adtID, 
                        $phoneNumberTypes->{'Day'},
                        $row->{'cust_phac'}, 
                        $row->{'cust_phpx'}, 
                        $row->{'cust_phsx'}, 
                        $row->{'cust_phex'}
                      );