to block junk cellphone messages
屏蔽垃圾短信

讲解：
屏蔽 to block.
例如：3 major telecommunication operators in China will jointly launch a technical platform to block junk cellphone messages.
我国三大电信运营商将正式上线运行网间垃圾短信联动处理平台，联手进行垃圾信息自主屏蔽。