Band: Caller: Dancers.
Caller is I/C: She/he should be able to tell the band the name of the dance (in case the band have a set they usually use) AND the rhythm, number of bars and pace (in case they don't).
Band: Should have an 'in rehearsal' repertoire that covers pretty much all of the rhythms and bars the average caller is likely to require. It doesn't matter what the tunes are called. With any luck they will also have a 'for listening' or 'not for dancing' repertoire that occasionally lets them show how good they are and give the dancers a rest.
Dancers: The band and caller have to work with they get!
If the above does not apply to the Band and Caller, they have no business taking money for doing a dance.
Just my opinion, of course!