I've tried multiple times, including contacting the corporate branch of the automaker and talking to multiple dealers, scouring the forums, and everything else in an attempt to disconnect my car from their online services (in theory, depending on the automaker, the hackers can completely brick your car).

My car isn't from Kia, but this is not unique to Kia. I eventually personally found the microcontroller and shorted the modem myself, after doing extensive work to figure out how to do it without breaking anything else.