Is there a command to remove previously installed package?
You can use pkgUtil for it. 

$ pkgutil --pkgs # list all installed packages
$ pkgutil --files the-package-name.pkg # list installed files


After visually inspecting the list of files you can do something like the following:

I leave this up to you as modifying files with root user maybe a bit risky 

$ pkgutil --pkg-info the-package-name.pkg # check the location
$ cd / # assuming the package is rooted at /...
$ pkgutil --only-files --files the-package-name.pkg | tr '\n' '\0' | xargs -o -n 1 -0 sudo rm -i


To remove directories as well as files, list the directories from the package using:

$ pkgutil --only-dirs --files the-package-name.pkg


The following command could be used to attempt removal of each directory, although be aware that when System Integrity Protection is active, there are some file paths that not even the root user may modify. Nevertheless — and needless to say — extreme care should always be taken when removing files with root privileges. 

$ pkgutil --only-dirs --files the-package-name.pkg | tr '\n' '\0' | xargs -o -n 1 -0 sudo rm -ir


Once you’ve uninstalled the files, you can remove the receipt with:

$ sudo pkgutil --forget the-package-name.pkg


For more details, see the pkgutil main page.