The frequency of calls I was getting about a year ago lead me to unplug the phone, resulting in complaints from relatives that they can no longer ring us. (I also have no intention of telling 90 year old grandparents to use a mobile instead). To resolve this I ended up setting up RasPBX on my Pi3 and configuring it so that whitelisted calls ring the home phone and everything else gets answered by Lenny, the calls are recorded for my entertainment and emailed to me on completion.
I went from being irrationally angry every time the phone rang (like Robert) to looking forward to the next scammer call so I could tweak the system and attempt to trap the scammers on the phone longer, this has kept me entertained and engaged for hours and I've learnt a lot about Asterisk and telephony in general as well.
Since first configuring the system I have managed to get the system to press 1 when an IVR call comes in in order to try to get connected to a human, and also randomly select Between Lenny, Astycrapper (Jordan) and the "are you there" child recordings.
Incidentally I have discovered in my fiddling that at least some scammers seem to be utilizing poorly configured (probably asterisk based) PBX's themselves, they seem to have the incoming calls being dumped into a conference type call they are already on and that the DTMF recognition is still turned on but without any actual error handling configured. I have had multiple calls where Lenny has incorrectly identified the speaker as a IVR robot and pressed 1 only to have the call suddenly disconnected by the remote end when the scammer PBX barfs on the DTMF tone.
I have wondered if you could look up the default Asterisk conference DTMF commands and find a way to cause greater disruption by shutting down the conference or conferencing in external parties (like the police) to the call vie the scammers PBX.