Problem with MagicPin

I opened magicpin to claim a deal..
Just then, I left it open in background for using a different..
And then within minutes it used all the data balance left from daily limit about 1.24GB.
I came to know about it only on getting SMS from jio about data exhausted..

My question is where the hell did it utilized 1.24 GB of data that too when I left it idle in background even without initiating any action.