i got a brand new 16gb ipad 4 not open yet. can i change it for a 32gb version with extra payment?

Welcome to the Apple Support Communities

If you have bought it less than 14 days ago, you can return it and buy the 32 GB version

Depends on where online you bought it. If from Apple.com, then the 14

day policy discussed by mende1 applies. If from other than Apple, then

the return policy of the online merchant applies. Don't wait to decide

what to do - the clock is ticking.

One you return for the money, it is just a question of what they have in the stockroom.