GPS only uses hardware chip to pinpoint your location. It has nothing to do with mobile data, unless you're using navigation, but in that case mobile data must be on.
Apps in the background or on the front can't turn on data without permission.
My data is off, and there is no data usage, Zong hasn't charged me for data usage. As mentioned in my original post, they enabled some games package on my number without my permission and it was not showing up in the My Zong app.
Only balance was dropping, so I called helpline and asked if there is any hidden packages enabled on my number. Thats when they mentioned "forest games" package.
If this wasn't a scam, they would have listed this package under MyZong app.
So anyone facing problems with balance dropping should call helpline and ask them if you're subscribed to any hidden packages.