Apple ipod

"I can put a SIM card in iPhone 3G?

I have the iPhone and the SIM card is a 3G card. if I bought the iPhone 3G could use my card old on the phone without 3G upgrade to the $ 30 data plan months compared with the old regime Currently I have $ 20?

No, you can not use your old data plan with iPhone 3G, which are to activate the plan is good to buy your iPhone 3G

Firemint tech demo: iPhone 3G vs iPhone 3GS