Ofcourse, sorry to hear about the difficulties. It is not a bad idea to try to attend one of his weekly shiurim, and speak afterward. However, if that is not possible, then it may take time. One thing for sure, is that the weeks before Pesach are the worst for any Rav. I myself who know him very well, never try to call during that time, unless it is an immediate and quick Pesach shayla.
If you can wait until after Yom Tov, may be best. However, if it is urgent, then maybe keep trying. Note, the secretary is not Jewish. This Rav always felt that having a frum, Jewish secretary means that people’s private matters may somehow get out into the Jewish community at large. He therefore bdvaka has a non-Jewish secretary who is unlikely to have any frum friends to whom she might unwittingly relate anybody’s personal info.