You have to practically be a lawyer to not get ripped off on rental cars. I really try to avoid them...just a scam.
With cell phones make sure to record an inspection with the agent as the star role. Make them acknowledge every scratch and dent and film the miles.
However... I usually find the cheapest place with pre busted up cars from Arabs or Iranians. They don’t care about the cars and cash is king. The ONLY time I use Hertz or Avis is when a company pays for it. Otherwise they are a huge ripoff.