(a) No common carrier in its operations as a common carrier may charge, demand, collect, or receive either directly or indirectly from anyone a greater or lesser compensation for a service rendered than from another for a like and contemporaneous service.
(b) The provisions of Subsection (a) of this section do not limit the right of the commission to prescribe rules and rates from or to some places that are different from rules or rates for transportation from or to other places.