I strongly suspect that this has to do with your company having negotiated a new rate with Hertz effective 1/1. As you are using your company's negotiated discount (CDP), quite legitimately, you are also stuck with whatever it is that they've negotiated.
Before you do anything, speak with your own travel / finance people and see if there are any changes effective the first of the year.
Quit calling multiple Hertz people. Neither you nor they have the authority to negotiate. I doubt that the local station will honor an expired CDP as this is a pretty standard thing worldwide and across the industry.