At this point, you need to get Hyundai corporate people involved. Look in your Owner’s Manual for contact information for Customer Care/Factory Zone Rep, or whatever they call the corporate people whom you can involve by calling a toll-free telephone number. With other manufacturers, it is possible to have one of these people meet with you (and inspect your car) at the local dealership. Whether Hyundai does this remains to be seen.
When a dealer’s service department appears to be unable to resolve an issue, or if they are simply “jerking” a customer around, it is appropriate to involve the corporate people. It should be interesting to see whether Hyundai is truly committed to customer service, so please post back after you have met with somebody on this problem.