So it’s common knowledge at this point that some scammers have systems which don’t automatically hang up which can be farmed for free credits. However, these, to my knowledge, are few and far between. An alternative of nearly equal value is to go to a number such as that found on oxiumsoftwares.com (my new pet project since http://scammer.info/d/22655-2-vms-chillin-in-a-host-machine-5-pixels-apart-cuz-they-re-not-gay) (+1-866-263-5737) and call while routing audio from a youtube video into the call. The voicemail detects speech, and leaves it up for 10 minutes at a time. With auto redial, this farms credits quite nicely.
You can do this with VoiceMeeter Banana (which, while I use it frequently, I'd be lying if I said I understood all the buttons), or, for the non techy, you can just watch youtube on your phone with full volume near your speaker.
Youtube: https://www.youtube.com/channel/UC9HxH2qIxvdY_IewWZ2BrGw/
Patreon: https://www.patreon.com/Alphactory
BTC: 1BtL9nboK7ZFbYb6FYS3tHCuHaTa2z1aRB
Destroy them.