I want to buy one from Ebay, but I would like to know if I buy it then use it through AT&T, do I have to buy and internet package?
Yes you can buy Blackberry Storm unlocked from eBay and use it with AT&T. But unlocked phones are more expensive than locked phones. So try to get locked phone and unlock it in order to save money. Use unlock code to unlock your Blackberry. Get the code from the site http://www.mobile-unlocker.com/blackberry-storm/rs2wp9/ and unlock it using unlocking instructions which is given in the site itself.
probly so, or get it put on your hone for 20-30 bucks a month