Wi-Fi info regarding my blackberry 8820

Hello,

I have the Blackberry 8820 with AT&T and had a question in reference to the Wi-Fi options with the phone. I do not have the data plan with my phone but it has wi-fi capabilities. Thinking it is free I had been using it with my home wireless and whereever else I was able to find free connections. I just got my bill and saw that I have been charged for browsing. I have settled the dispute with them but have now learnt that I am unable to use the wi-fi unless I have the data plan. Is that true? What's the use of the wi-fi then if we cannot use it without the data plan. There is a hotspot browser option on the phone but that too excepts the data network to be turned which I have currently disabled on my device. My question then, can I use it the ninternet on my phone with my wi-fi without being billed for it. It was the sole purpose I switched from Verizon. I know T-mobile carriers have wi-fi phones and can use it for free, so why then does AT&T not allow us to do so?

Someone please help!! :(

Thanks.

Anil