Driveclub Free Upgrade not delivered.

The information on the website of Europcar Driveclub states that a customer will get a free upgrade on every 3rd rental but i booked my 3rd rental and then i did not get my upgrade after putting much efforts of calling the customer service to confirm my upgrade. I was just told that they will call me back but the lady didn't call me back and i ended up collecting the vehicle from the group that i did not want because at the branch they couldn't assist me as well. I was so disappointed with this. Why do they put a benefit that they cannot deliver?