What would a bad transmission sensor do to a 2001 Kia Optima?

My car was having transmission problems and the dealer said I need a new transmission sensor. Here were the symptoms the car had: When traveling around 55-65mpg the car would make a single violent jerk then the rpm's would shoot up to 3000. It was like the car was in a higher gear then it was supposed to be in. To correct the problem I would stop, turn off the car, place in park, and then restart.

You know my car is doing the exact same thing as yours I just want to know if that means the transmission is giving away because I got the sensor replaced and it did not fix the problem so I am as well having to shut it off and turn it back on