Unlimited internet surfing with a usb internet stick

Internet sticks are the craze today, and the battle for having the fastest connection is now making the waves on tv, radio and internet. I just discovered months ago with this one branded internet stick, I'm using it completely FREE and it runs in unlimited internet surfing time. It is weird, and checked the load of my prepaid sim card and it says ZERO. 

I won't mention the brand of the internet stick that I'm using, and to make the clue worst, I'm using three different kind of internet stick with different brand names. I guess this will be a big scavenger hunt to know which internet stick is having flaws detecting your zero load credit and let's you connect to the internet. I just discovered this by accident and I think there's a system error after the Ondoy tpyhoon that makes you connect to the internet. It's been a month after my discovery and a weeks after my last log in, I just don't know what happened and I'm planning to replug it again to check if it will give me free internet load time in my zero credit account.

Have you experienced this too? if yes, please share your experience.