ictdialer
Open source auto dialer for voice, fax and SMS campaigns
...IVR flows are built with a drag and drop designer rather than written by hand, which matters when the person designing a survey or a press-one campaign is not the person who administers the switch.
GPL-3.0 licensed, with Docker images published for the application and for the ICTCore engine underneath it.
Note that this open source edition runs on FreeSWITCH. The hosted commercial service of the same name is a separate product built on Asterisk.