How do I reset proxy in terminal to automatic if not connected via proxy

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http://askubuntu.com – Well,all I ever wanted was to download and install an application from the terminal. And to my surprise I just can't I tried to reset proxy of the terminal by some commands but it doesn't happen and automatically switches back to this proxy (which apparently was my college proxy). I checked in my system settings too.. I don't understand why this is recurring. Please be comprehensive,I am a nube :) Also I further would like to know how to bypass proxy server since I couldn't access any of the repositories as they were blocked in my college's proxy settings as is Ubuntu's homepage. (HowTos)