If this is an image, you can check this article for more info on how to try to resolve the issue.
For regular text messages, your carrier is simply delivering that message multiple times. Pulse SMS will strip out duplicates that you receive within a minute of each other, but will save the messages in any other case.
Duplicates are not uncommon for SMS, since it is a legacy protocol and not as reliable as more modern messaging frameworks. If you are seeing this, you could try to just restart your device.