You can call from Jeju Island, and the traffic doesn't matter.

According to Ma Honeycomb's inquiry, the telephone traffic in Jeju Island is unavailable for the following reasons:

1. Signal problem: If the signal in your area is not good, you may not be able to use the traffic. You can try again where the signal is good, or use the wireless network.

2. International roaming: If your mobile phone does not have international roaming, or the operator does not support international roaming in Jeju Island, it may lead to the inability to use traffic. You can contact your own operator to open international roaming service, or buy local calling cards or traffic packages after arriving in Jeju Island.