how long does it take before att automatically charges you for a data plan?

[Bill L]

I just received a blackberry 8900 from a friend and after a day of using it, it automatically added a $25 a month plan. I called and got the plan removed but they said i can't use the phone without it. Now i was wondering if i could just switch back a for between a the blackberry and a non smart phone like at night or something cuz it seemed it took an entire day for them to charge me the plan. Is this possible? Will they catch on? How long is it before they add the monthly plan back on