Question on a wifi/internet topic

I had my internet connection to my phone blocked so i wouldn't accidentally surf the web in my pocket, but i recently got wifi so i decided to test something out. I still had my internet connection blocked to my phone so i wasn't able to get on the internet, but when i connected to wifi i was able to go surf the web. My question is whether this is free or not, like the ipod touch, or do i still have to get a data plan on my phone. I'm worried that if i do use this method to surf the web on my phone that i might get a big bill from hidden fees or something like that, so if someone wants to try this or has done so before please tell me if this is safe to use

thank you for you time =D    

i called sprint and told them to block off my internet connection (because i didnt have a data plan, to avoid getting charged with a huge bill) no registry hack, or app. thanks for your answer, i just wanted to know so i can let my sister play on the computer while i watch videos/surf the web on my phone =D