You did call Member Services, because they are the only ones that can give you the member discount.
I have gotten it several times, its 25% off of the rack rate. I was lucky I guess and got it when I called. So keep trying and something else I learned that I did not know.
When you book the cash discount, they will ask for a credit card to hold it, but they don't charge a deposit, unless you are a no show without the 5 day cancellation or when you actually check in.
I kept looking for the one night charge on my account after making the reservation and it never showed up.
Learned something new.