You're plugging into a computer? Get a power-only cable for that. If you're plugging into the charger, there's a defect in the charger, the cable or the phone charging port, making it think that something is connected to the data wires. If you can't see what and blow it out (or very carefully remove it with a wooden toothpick), it has to go to a repair shop or you have to keep looking at the message.