The warranty don't do you much good unless the dealer is willing to listen to you. I have complained many times and they always say it is normal. the engine does not have a thermostat, temperature is computer controlled. The next nearest dealer in my State is 100 miles away. Never will buy another Kia.This has been cussed and discussed before. In park or neutral you cannot rev your engine past 'About' 2k rpm. Revving up any engine, with no load on it, is very harmful, and your KIA Soul is smarter than you are, evidently, because it won't let you destroy it.
On the coldest days we've had here, at or even below freezing, my heater is blowing HOT air before I can get out of my neighborhood.
If yours won't, stop griping about it, and go get it fixed. That's what warranties are for.