How to change text tone for Blackberry Curve 8520. you can custom your Blackberry Curve 8520 text tone and ringtone.
To change Blackberry Curve 8520 text tone, from the main menu go to Profiles (you may need to hit the menu key to find it if it is not on the main page) and select Advanced. Then highlight the current profile (in bold) and press the menu key and select Edit. Then click on SMS Text and you can select the ring tone from there.
To change Blackberry Curve 8520 ringtone: Press the BlackBerry key > select Media > select Ring Tones > Scroll to All Ring Tones, press the Trackball > select the ringtone you want, press the BlackBerry key > select Set As Ring Tone and save.