Please check the following information.

• SMS can only be received by phone numbers starting with 090, 080, or 070. Fixed phones, some budget smartphones, and oversea phone numbers are not available.
• Please check that your phone number is correct.
• Please turn off the Wi-Fi setting.
• Please check that your contract and smartphone/cell phone are able to receive SMS.
  The network may be unstable, so please take some time and try SMS authentication again.