In order to save battery power during calls and texting, try this. Go to main menu System, select Settings, select Phone Setup, select last item Misc Setting, you can jump to this last item by using the main button and press up. Then select LCD Backlight. You will see two ranges; One for Brightness and the other for time. Lower the brightness by sliding or touching to the left of the green button (with arrow) to lower the brightness of the Backlight. Next, do the same to reduce the Tme/duration that the light will remain on. Now select Ok. Next, select KeyPad Backlight Setting and you will see two buttons Off and On. Select off, then Ok. Now you can exit Settings. You do not need light during the day to see the Navigating buttons so this saves you battery power.
Edited: This is the manual way of customizing your setting. For those of you who don't want to go through all this. Go to System in the menu and select User Profiles. Now select Power Saving, then Option then Activate. Now, if you want to use your customised ring tones, you will have to go back to Option and select Customize and manually set each item on the list. Have fun.