motorola moto g – How to block spam by SMS

I use a MOTO-G6 and it works on Android-8.0.0. The default SMS application is Google-Messages.

I'm getting tons of annoying SMS spam from unnumbered contacts.
It just shows a name for example:

VKHLTCHK
HPFAMDOC
HPYESBNK
...
...

I can block these contacts, but I always get sms over and over again.

Does any one have this kind of problem? How do you solve that? I am ready to buy a paid application if it exists.