> I've never seen an hotline where you can call back and resume the call you were doing.

Assuming they even accept inbound calls to the CLI number in the first place.

I frequently encounter companies where I miss a call due to $reason, I then try to call back the CLI number and it just says "This was $megacorp trying to call you, we will try again later".

Or, if you're really lucky, the CLI will just dump you into IVR-hell which, of course, is "AI powered" today, so you have to spend 30 minutes telling the stupid robot they mis-intepreted your voice.

My electric company gave me a number (UID, not phone number) to resume a call if the issue wasn't fixed within 24 hours, and I'm pretty sure internet operators have the same protocol (at least used to).

The call centre for my Australian bank's KYC is seemingly backed by a single person. I've spoken to her a few times now... so calling them back more or less does work, though you might have to wait on hold again.