Upgrade from Ubuntu 12.04 to 12.10 with the iso on USB flash drive

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http://askubuntu.com – How do I do an upgrade to 12.10 using the iso downloaded from the ubuntu web site? I do not want to do a clean install as I do not want to loose my settings. I am afraid that clicking "UPGRADE TO 12.10" in update manager will upgrade the OS and all the packages and that this will take all my monthly data from my contract which is just 3gig a month. (HowTos)