x475 - inbox memory

First post, tried searching, but found nada.

Just picked up a Samsung x475 and it's pretty cool. Only question I have so far that I can't seem to find in the manual, is how to get it (if possible) to save text messages to the phone memory instead of the SIM card?

Sim has 30 slots, Phone has 200, but I can't find the menu to change this anywhere.

Anyone have any advice?

Thanks.