Hey guys, I just hung up with AT&T. I called them about my bill which went up this month for unknown to me reason(and I'm not using internet-EDGE). Meanwhile, I had EDGE disabled from Boss prefs. When I asked why is that, CS told me that I have data usage. I said that I'm kinda confused and right away she told me that she can disable data services for my 2 wireless lines. She credited my account, made a test that data is not going through and then we hung up. Right at that second, the E icon on top let (next to carrier logo) disappeared and now my EDGE is finally trully disabled.
We were discussing Boss prefs once and I remember someone said that E icon is always there, no matter if you turn the service off or on from Boss prefs. Well, apparently it's not true. You really have to call AT&T (or your carrier) and request this to be turned off in order not to get charged for data usage.