You need to check your data balance.
Even if there is data, if you cannot use the internet, you need to set up NEW APN as below.
* How to set up new APN for ANDROID version
Please go to menu>settings>mobile network>access point names>new APN. And input as below.
- NAME: KT
- APN: alwayson.ktfwing.com
- MCC: 450
- MNC: 08
- MMSC: http://mmsc.ktfwing.com:9082
After saving new APN, please switch off & on your phone several times.
* How to set up new APN for IOS version
If wifi is available, please run "Safari" and access to "http://www.unlockit.co.nz"
After access, please choose [Create APN], and then select mobile carrier as "KT"
And press [Create APN] button, and there will be the message "Installation of Profile"
Please install it and then reboot your device. Then you can access to internet.