Aside from a pair of very ridiculous incidents with Sears and Dish network, my two worst consumer experiences were with American Express credit cards and the American Express brokerage.
I'm sure others had good experiences. Mine were likely exceptions. But even when they made huge and ridiculous errors, they fell down badly in correcting them.
My favorite though, was when I finally left Amex brokerage. I had them transfer my mutual fund holdings (all one family) to the fund family for holding. They transferred ALL of their holdings in that fund family into my account: mine and all the rest of their customers. I forget how much it was, but it was tens of millions of dollars. Of course they took it back. But I still have that statement somewhere, and its fun to look at.