Try being a business where you are obligated to answer the phone in case it's a customer. We easily average a hundred junk calls for every one valid customer call.
I have taken to speaking like a robot, repeating two sentences in a loop ("You have reached technical support, please describe your issue." -> "I am sorry, I cannot deviate from the technical support script. You have reached technical support...") until the spammers come to the realization they cannot manipulate me into giving an affirmative response that they can interpret as consent to move our phone service, subscribe to service offerings, etc.
They have made phone service effectively worthless, just as they have made all other forms of communication effectively worthless.
Edit: Just remembered something else I do: I do not answer the phone with "Hello" or anything like that. The vast majority of calls that we receive are originated by an autodialer that is listening for a typical greeting so it knows in what language its payload should be delivered. Instead, I answer with only the name of the business and nothing else. If I hear silence, I repeat the name of the business. After a short time, the autodialer gives up and terminates the call.