You can download the Xiaomi Contacts and Dialer APK from trusted repositories like APKMirror . Note that these often fail to install or crash on Global ROMs because they lack the necessary system frameworks.
Xiaomi does not publish its stock Dialer, Contacts, or Messaging apps on Google Play. These are system apps pre-installed only on MIUI (and now HyperOS) devices. They depend on Xiaomi's framework and permissions. miui dialer play store
A custom dialer allows Xiaomi to: