Haven't seen this being answered before - I want to book my wife and son on the BKK/KUL fare ex AMS

What happens when I call? Do I quote the fare basis code, plus the flight numbers and times, or do I just reel off the list of flight numbers and assume the fare will work itself out?

I assume that for an ex EU fare I pay in Euros? Any best time to call?

Thanks - want to get this booked fairly soon and a bit inhibited by trepidation about the call.