There is a 1 on the i9300 SMS icon.

There are usually unread messages. Click Open to view them. If not, please remove it as follows:

Try to clean up the information software cache.

Settings-Application Manager-All Information-Clear Data.

If the above operation fails, you can try to back up important data, restore factory settings, and eliminate the influence of third-party software.

If the problem persists, it may be a system problem. It is recommended to send the mobile phone to the nearest after-sales service center for testing with the purchase invoice and three-guarantee certificate.