I rescheduled my husband's ticket from Jakarta to New York, but no response from the airlines

I bought a return ticket Jakarta-New York-Jakarta for my husband. I need to reschedule the departure date from JKT to NY. It is advised to do on line, and the confirmation will be emailed within 24 hours. Up to this date there is no response from the China Southern Airlines. Is there another way to reschedule the date of the flight?
Diah from United States