You can uninstall or removes an installed gnokii-smsd-mysql package itself from Debian 8 (Jessie) through the terminal,
$ sudo apt-get remove gnokii-smsd-mysql
If you would like to remove gnokii-smsd-mysql and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove gnokii-smsd-mysql
If you use with purge options to gnokii-smsd-mysql package all the configuration and dependent packages will be removed.
$ sudo apt-get purge gnokii-smsd-mysql
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 gnokii-smsd-mysql