You can uninstall or removes an installed gmessage package itself from Debian 7 (Wheezy) through the terminal,
$ sudo apt-get remove gmessage
If you would like to remove gmessage and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove gmessage
If you use with purge options to gmessage package all the configuration and dependent packages will be removed.
$ sudo apt-get purge gmessage
If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.
$ sudo apt-get purge --auto-remove gmessage