Please follow these steps to enable caller ID on your Mi4i:
Phone Settings -> Additional Settings -> Battery -> Manage apps battery usage -> Choose apps -> Eyecon -> Custom and in Background Network , choose stay connected.
If that does not work, please try the following:
Phone settings -> security -> permissions -> Eyecon -> allow all permissions.
After that, go to additional settings -> battery -> manage apps battery usage, by default it is “standard” make sure to keep it off