Without a deadline of some form, when do you escalate to public knowledge so customers can know they might get defrauded in some capacity?
You set a deadline after an initial conversation and urging them to fix it, if they don’t respond. I think the idea would be to escalate slowly. Like the original poster said large tech companies like know how to do this and streamlined the process. But, to someone not familiar with the process it looks like threats and deadlines imposed by a random person.
I am not defending the company just presenting their possible point of view. It’s worth seeing things with their eyes so to speak to try to understand their motivations.
It all depends on the goal. Is the goal for them to fix it most of all? To get them embarrassed? To make a blogpost and get internet points?