Car Rental insurance with Chase Preferred

To qualify for primary insurance you must decline the car company's collision damage waiver (CDW) or similar loss/damage waiver. How do you do this? I find that most car companies i've looked at (Alamo, Hertz, etc) include it automatically and there is no place to decline it. I also read on a reddit thread that someone had to show a letter from Chase that said Chase provides primary insurance through the credit card, in order for the car company to waive the insurance which they refused to do at first.

Anyone has experience with this? Ps. I'm hoping to book a car rental in Italy. Thanks all