There are several legitimate reasons why this might not be covered under
warranty, but the dealer should be able to explain the reason. I.e., the
dealer should be able to show that there is some evidence that the problem
was not a defect, but collision damage, improper workmanship by someone
other than the factory, etc.
Calling Hyundai's customer assistance line will create a case file which
will in most cases be sent to the dealer which serviced your vehicle. In
most cases it will get the service manager at the dealer involved, and in
some cases, it will get the factory representative involved. At the very
least, it will put some pressure on the dealer to tell you why the repair
wasn't covered under warranty. On the other hand, simply calling and
speaking to the service manager about the fact that they haven't provided
you any explanation could very well produce the same results.
I don't know a great deal about the class action settlement, I wasn't a
Hyundai tech at the time. I was under the impression that customers were
able to choose between extending their bumper to bumper coverage to 6/72
or taking the credit on service, but not both. I've seen several 6/72
vehicles and have heard of customers having a debit card for Hyundai
repairs, but I've never seen the powertrain warranty extended to 12/120.
I would think Hyundai customer assistance should be able to help you sort
this out. A simple vin check will advise of any warranty abnormalities
(such as the 6/72).