What kind of enquiry do you have? If it is a specific Worldperks and reservation related question you can just ask the Japanese agent to talk to you in English (I was told that they are not allowed to transfer your call to other agent).

If you are not satisfied, ask for English speaking Japanese agent to call you back. It worked for me.

All enquiries that do not need monetary transaction can also be made to the US elite line, their number should be listed at the back of elite card. US elite line could not process Japanese credit card, so cannot do payment for ticket reservation to US elite line, but can do reservation, itinerary change, etc.