Depending on where you live, you may have a gov't entity you can report this to that will scare them into handling it properly.

Slap that spam button until they get their spam scores crushed.

I've seen more than a couple "accidentally" broken unsubscribe processes

Unique emails for every service + blackhole for any time that stuff like this happens, breaches, sale of data to other entities... I've been doing this for almost a decade and it's wonderful being able to go "no u" and deal with the situation immediately.

Use filters, if you want some legitimate communication but not their bullshit, though I've only put up with that once and am no longer a customer/account for that company, so in my experience, just rip the bandage off and be done with it.

ah... KLM.... most hated company.

this is how you get 100% of my attention to social engineer your company into giving me the email and phone number of your executive board.