u/Cadet-Cryyx

Apologies if I flaired this wrong, but to get spam callers to hang up on you, and frequently not return calls, as it's worked for me, speak enough english to get through the bot, then speak in fast or exaggerated german. I'll bet other languages work to, maybe not spanish though, cause a lot more people speak spanish than german.
ex of a typical call:

me: hello?

bot: hello my name is *fake name here* and I'm calling to make sure you're getting your benefits. Do you have medicare part a and b?

me: yes

bot: I'll transfer you to one of our specialists now

*transfer*

real person: hello my name is so and so-

me: WAS? WAS SAGST DU? HALLO? ICH SPRECHE KEIN ENGLISCH! (or insert variation depending on how I'm feeling in the moment, could be polite, could be loud, exaggerated, could be gibberish or coherent.)

real person: either hangs up OR 'you don't speak english maam'

me: nein

real person: is there anyone who can speak english or help you speak english

me: nein

*click*

yippee! now you've wasted their time and practiced your language! This is wildly entertaining to me.

edit for clarity: I do this on a shitty old landline from like the 90s, my family thinks its great fun, and it helps me practice german.