Call blocking apps like Truecaller or Hiya are used by millions of people to protect themselves from shady calls.
Go to your device’s dialer, select the number that made the call and add it to the blacklist.
Go to the settings menu and activate DND mode. Once done, select All Contacts from the Allow Calls Section.
Registering your phone number on mobile operator specific DND registration websites might significantly reduce the number of spam calls you encounter.