Automatic Transmission Control Module problems of the 2011 Kia Motor Soul

I purchased kia Soul plus with automatic transmission 2 months ago from original owner with 53,000 miles. Vehicle "lagged" momentarily while transmission upshifted. I assumed characteristic of car. Approx. 2 months after purchasing car while driving on freeway with my fianc�' @ approx. 65mph the transmission suddenly & drastically downshifted into (I believe) 2nd or 3rd gear, with no provocation on my part. If my fianc� and I were not wearing seat belts, the sudden change of speed, our heads would have certainly hit the front windshield. My fianc�' is scheduled for spinal cord surgery sometime this month (August). Her neuro-surgeon informed us that another similar situation could possibly cause her to be quadriplegic, or even death. I immediately exited freeway, however, car would not shift past 2nd (or 3rd) gear, limiting car to 30 to 35mph driving home on side streets. Car was parked overnight, and next day drove normal again, for one week. On July 31, 2017 while taking car to citrus kia in ontario, CA, for evaluation of transmission, vehicle did same thing again. Sudden downshift drastically slowing down car to 35mph. Again, would not shift past 2nd (or 3rd) gear. I was only occupant. Aware of kia's TSB #033 outlining tcm's upgrade on transmissions built prior to Aug. 2010, (mine built June 2010) the service writer at citrus kia stated upgrade was done in oct. 2010. I am anxiously awaiting their findings. Hopefully today. (8/1/2017) kia's powertrain warranty is 100,000 miles or 120 months to original buyer, subsequent buyers is 60,000 miles or 60 months. Soul is past 60 months warranty limit having 72 months of service. However, under mileage limits at 56,000 miles. The vehicles transmission problem is most definitely a safety issue which needs to be addressed. Thanks for your time and consideration!.