New Zealand's time zone is GMT+12, or two to four hours ahead of Australia. If you are calling in the late evening, your contact may be asleep. To reach an organization in New Zealand before closing hours, you may need to call in the morning or early afternoon.  New Zealand is two hours ahead of Sydney, Melbourne, and Brisbane (which are on AEST). It is two and a half hours ahead of Adelaide (ACST), and four hours ahead of Perth (AWST).  New Zealand observes daylight savings time, but parts of Australia do not. If you are in Queensland, the Northern Territory, or the Australian Capital Territory, and you are calling between October and April, add one additional hour to find New Zealand time. Because callers are typically still charged when calling toll-free numbers from a different country, some businesses block international calls to avoid causing their customers unexpected fees. In New Zealand, toll-free numbers typically begin with 0508 or 0800. Try to find a regular, non-toll-free number for that organization by searching online, or contact it by email. Some phone plans block international calls. Try calling a different international number. If it does not go through, contact your phone service provider and ask to change your plan. Note that international calls are often significantly more expensive than local or in-country calls. If you call abroad frequently, ask about a plan with a reduced international rate.

TL;DR in Indonesian:
Pertimbangkan perbedaan zona waktu. Periksa apakah nomornya bebas pulsa atau tidak. Pastikan paket telepon Anda memperbolehkan panggilan internasional.