If I buy a Blackberry from ebay and i dont tell at&t that i have a Blackberry will i get charged?

If you don't want a data plan then just get a prepaid mobile. This is a mobile phone with no contract, you can buy them from any phone shop or on the internet, and you just pay a one off payment.

Whenever you put your SIM card in the phone it will automatically know what it is operating on. It isnt something that is going to take awhile, it will know instantly as that is how SIM cards operate. Hope this helps! Dont mean to be the bearer of bad news, but I have been there and done that! :)

Just be aware that at anytime at&reserves the right to add that data plan to your account. If you want to avoid that I recommend you buy an unbranded phone that is unlocked and will operate on the At&t network

If they find out, they will indeed. They will backcharge to when they can identify that you began using it. All carriers now charge a smartphone data fee. Blackberry is a smartphone. Thus the charge.

The $30/month data plan will be add to your account as soon as the network detects you're using a blackberry. The data plan is required. If you don't want it, don't use a smartphone.