Pathetic after sales service from Hyundai Woodmead and no cash back received a month after purchase

I purchased a Kona from Hyundai Woodmead and tool collection of my vehicle at the end of January. I was then informed that my cashback would be paid out to me within 7-10 days. We are now on the 1st of March and I still have not received even after numerous calls and follow ups. There are plenty of excuses made and when contacting the dealer principal, my calls don't get returned, the sales person is constantly telling me that it's on the screen , whatever that means, I have to call him about 7 times today each time he says he's going to call me back and he doesn't. Then I get told the accounts department needs to process it, at the end of the day the accounts department says head office needs to process it and when calling head office they advised that they do not deal with cash backs the branch does. To top it all it took 27 days for hyundai to settle my old vehicle, of which an amount was debited off my account for interest incurred due to the fact that Hyundai could not settle my vehicle intime after I issued them with 4 settlement letters after each time one lapsed. It's easy to take the money from the bank as the full amount was paid, but when getting my cashback excuses get made and the blame gets shifted from pillar to post. Totally pathetic service . I want this sorted out asap .