Duplex is the strikingly realistic voice-enabled arm of the Google Assistant. It can carry out tasks such as booking tables at restaurants for smartphone users in 43 US states. It had been restricted to doing so on Pixel-line phones only; however, an XDA contributor has claimed that it may now work on devices from other OEMs.
https://www.notebookcheck.net/Google-Duplex-is-now-migrating-to-phones-beside-Pixels.415751.0.html