will it be possible to use the iphone 3g as a backup phone to iphone 4?

[macaco74]

I am guessing not since the sim card is a different size. Does anyone know?

 

[j3yq]

your more than likely right unless they make an adaptor.

 

[grapes911]

A 20 second google search found this. Seems to solve the problem. I'm sure you can find some in English if you tried.
http://microsim-shop.com.ua/Details.html

Edit: 20 more seconds of searching I found this one which is a little more readable:
http://www.microsim2sim.com/