Please find the file called 'version.php' in the root/home folder of your Moodle installation and tell show us its contents.
If you can, open the database browser that came with your hosting, find the table in your Moodle database called 'mdl_config' and find the entry where name='version'. Show us the contents of that record please?
If the version from version.php is *older* (version number is lower) than the one from the database, the message is true and you have got hold of an older version of Moodle than you had installed before. That message is almost always correct.