i feel what u wan is not only to know who call him and also what is their relationship. But do u think he will ever tell u the truth if he is having affair with that person.we still not talking N I wont allow him to sleep inside too until he tell who that person, so urgently call N call N even talk to the person the whole night too.
I would suggest to you, don't alert him. Let him think u get over it then, secretly do some check.