This app reviews incoming calls, and can be set to reject all unknown calls (including all numbers which aren't in your contacts). To download it, open the Play Store, then do the following:  Tap the search bar. Type in should I answer  Tap Should I Answer?  Tap INSTALL  Tap ACCEPT Tap OPEN in the Google Play Store, or tap the octopus-shaped Should I Answer? app icon in your Android's App Drawer. It's at the bottom of the screen. You'll find this at the top of the screen. It's near the middle of the Settings page. Tap the white switch to the right of any (or all) of the following:  local negative rated numbers community negative rated numbers numbers not stored in contacts hidden numbers foreign numbers If you want to prevent unknown/non-contact numbers from being able to text you, scroll down to the "Block INCOMING SMS" section and tap the white switch(es) next to the option(s) you want to implement. Your settings will be saved. From now on, calls from unknown numbers should be blocked.

TL;DR in Chinese:
下载“要不要接听？”应用程序。 打开要不要接听。 点击继续。 点击设置标签。 向下滚动至“拦截来电”。 启用来电拦截功能。 如有需要，可以禁止接收短信。 退出。