https://purengom.com/2017/10/27/mvno%ec%97%90-%eb%8c%80%ed%95%ad%ed%95%98%eb%8a%94-%ec%9d%bc%eb%b3%b8-mno%ec%9d%98-%ec%9e%90%ec%84%b8-%ec%9d%bc%eb%b3%b8%ec%9d%98-%ed%86%b5%ec%8b%a0-%ec%96%91%ea%b7%b9%ed%99%94-2/