We have found a solution to the taped/computer (ie non-human) spam calls — via youtube, play the “disconnected line” signal/message. After you hit a few of the taped calls, the spam calls stop.
My mother-in-law has a way with human spam calls... she starts gibbering in “Chinese” such as wing-wow ye-how(modulated low to high pitch). I suppose you could learn an insult phrase in Hindustani and use that!
I’ve actually gotten spam calls in (apparently) Chinese.