Mall information service

I am trying to get hold of O'Brien and D'Arcy Jewellers in N1 City Mall, but all the numbers listed fails when I call. I phoned the Mall information desk, they were not helpful at all. Just told me that the only number they have, and that's it. I asked if they have an email address or an alternative way to get hold of them, and the lady just said no. Not good customer service at all.