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).
> My electric company gave me a number (UID, not phone number) to resume a call if the issue wasn't fixed within 24 hours
What planet do you live on ?
Seriously. Where I am it is guaranteed that a utility company would never even consider such a concept let alone have the technical competence to actually implement it.
> 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.
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.