> So, if I use my SIM card 16 hours a day, 7 days a week, Ill get banned?

Probably not - you'll get billed or hit a FUP

> Doesn’t that seem absurd? The SIM card is enforcing one voice call at a time. If the apartment building has to wait in line to use it, what’s the difference?

The difference is that it is perfectly acceptable to enforce a "no-reselling" or a "no-3rd-party" for services.

I can't think of a single service provider that provides a consumer tier permitting reselling or 3rd-party use.