Arduino Uno WiFi - How to disable WiFi?

I'm using Arduino Uno Wifi. I made my Arduino to get connected with my local network based on http://www.arduino.org/learning/getting-started/getting-started-with-arduino-uno-wifi

Now I would like to disable it and work with USB serial communication to upload sketches. But now I'm unable to upload sketches when I select the serial port of the Arduino. I'm getting an AVRDUDE : seropen() Access is disabled error. I could perfectly do uploading if I select the networked port of the same Arduino.

Can I know why ?