Inconvenience of 2 cell phones

As the military camp does not allow the use of camera phones, I have to resort to switching between my old Nokia 6610 on weekdays and my camera phone on weekends. Not only does this bring great inconvenience everything I make the switch, I have to ensure that my contacts on both phones are synchronized. This can be a hassle as I have to manually take note of which contacts have changed and copy it to my SIM card so that I can recopy it to my camera phone while making the switch.

Thus, can anyone please advice if there are any other easier methods? Note that most new phones store its contact information on the phone instead of the SIM card. Yes, I can still view my contacts from the SIM card but it is more troublesome.