Can you provide more information about the beeping noise you are hearing?
It's possible that one of the doors on your Sorento is not closing all the way. Even if you have the locks on, if one of the doors is not properly sealed, the car knows that it's not completely shut and will beep at you. If the sound is intermittent, there may be something leaning against a door that could be loosening pressure on the sensor while your vehicle is in motion.
I recommend you open and close every door to make sure they are indeed closed. If it is still beeping at you then you may want to visit a repair shop to figure out if there is something wrong with one of the doors or if something is wrong with the indicator system.
For additional assistance, please find an AskPatty Certified Repair Shop at http://www.askpatty.com/search/?type=all&m=30&q=&keyword= and they can help you diagnose and repair the problem.