Where is a sms blocker in settings?

Avast Mobile Security Avast Mobile Security for Android
1

I have found only call blocker

2

As far as I know there is no such thing.
But if there is you will find the info in the FAQ.

3

Hi, the SMS blocking has not been available for quite a while now, as it has become technically impossible for us since versions 4.4 and higher.
Thanks for understanding.