2GB Nigt Owl

Before i swithed on my data for night owl i looked to see how many data i have. About 00:08 i connected to play store, searched for games and strated to download one. This morning around 02:30 Night owl used 400mb from my normal 2GB data. Is this a **** ? If i dont complain it will just go by? Or do i have the wrong impression about night owl. How many people just let it go without complaining. Vodacom score money all the way. This contract feels like i was misled by their adverts