Maybe it's just a difference in interpretation of language, but for me, a fast food joint is definitely NOT a restaurant. The tone of the story also clearly implied it was an actual restaurant, nothing fast about it.
I'm not sure where you're from, but in the united states, employers can pay an hourly rate of $2-ish to people who are expected to collect tips. The stereotypical fast food kid actually has a better hourly rate.
Since when is the definition of a restaurant worker someone who does not make much money? Especially those not working fast food?
Naturally this only applies to the waiting staff, but then again, the chefs aren't going to be the ones handling your phone.