It ensures that common carriers can’t “make any unjust or unreasonable discrimination in charges, practices, classifications, regulations, facilities, or services.” (Title II, the second subsection 202). Classifying these ISPs as title II / common carriers gives the FCC the ability to enforce net neutrality.
Some further info, from wikipedia's entry on common carriers: A common carrier in common law countries (corresponding to a public carrier in civil law systems,[1] usually called simply a carrier) is a person or company that transports goods or people for any person or company and that is responsible for any possible loss of the goods during transport... A common carrier is distinguished from a contract carrier (also called a public carrier in UK English),[2] which is a carrier that transports goods for only a certain number of clients and that can refuse to transport goods for anyone else, and from a private carrier.
A common carrier holds itself out to provide service to the general public without discrimination (to meet the needs of the regulator's quasi judicial role of impartiality toward the public's interest) for the "public convenience and necessity
And I'm sorry are you honestly claiming that those cost 20% of an internet bill? Because of so you're gonna have to cite a source for that one. Between your selective choice for what you claim is CC status, combined with a claim that a $50 monthly bill is $10 attributable to CC, makes me think you're pushing an agenda rather than sharing facts.