This is a regular verb. It follows the conjugation pattern of the verb hablar.
PresentPresente
El público calla cuando empieza la película.
The audience goes quiet when the movie starts.
ImperfectPretérito imperfecto
Los niños callaban cuando entraba la maestra.
The children went quiet when the teacher came in.
Negative ImperativeImperativo negativo
Si algo te molesta, no calles.
If something bothers you, don't stay silent.