And I'm saying that even if the customer support knows about the call, that doesn't mean that the next call you get in 2m from the bank is legitimate.

In all cases, anyone reaching out to you from your bank should be treated as not legitimate. The only way to do this is to call the bank yourself, and get put through to the person who wants to talk to you.

Any other way including the way you said you'd do it is vulnerable to phishing.

I'm saying that checking with the bank doesn't indicate that a call was legitimate, so there's no point in checking with the bank.

If you call the bank, using a customer service number that's already known to you, either they will say there's an issue with your account or they won't. So calling them does tell you, indirectly, whether the previous call (that you hung up on and gave no information to) was legitimate or not. But more importantly, it tells you, regardless of the status of the previous call, whether or not there is an issue with your account, and that's what you care about.

Note that you never have the bank call you back in this scenario. You call them, and that's it. You don't call them and ask them to call you back.