Samsung SYNC SGH-A707

how does the SYNC perform as far as RF in a GSM/EDGE-only zone and is there a way to put the SYNC in GSM mode with a menu option, i live in a 3G area, im just curious if i can put it in GSM mode if i wanted to do it, and i know it can be done automatically but i want to know if someone can manually do it as u can on the CU500