Transmission Gear Slipping problems of the 2015 Chevrolet Tahoe

Tahoe 2015 LS transmission is slipping into neutral during acceleration from a stop sign/light after cycling through 1st and 2nd gear. SUV will slow down in traffic. It also auto shift into park like condition at traffic light and would not move forward. I had to place the shift lever into park and then back to drive to get the transmission to engage. It also kick hard when engaged. The SUV only has 5089 miles on it. I bought this SUV new from reliable Chevrolet in richardson, TX. Today the problem got worse. It now would not engage when I put it into reverse. I had to push the gas peddle more to increase the rpm to get the transmission to kick in. It then kick hard into reverse. I brought this SUV to my dealership to get it fix. They said they found nothing and return this SUV back to me. I have another major stop and no go transmission issue again today Feb 8, 2016. This time I have my teenage son with me and this really upset me. Someone could have hit me from behind since the road was a downhill run with a stop light. I am bringing it back to my reliable Chevrolet dealer in richardson, TX tomorrow Feb 9, 2016 and demand then to fix it. I am now afraid to drive my new truck. If the electronics of the transmission tells the mechanical parts to go into park position while cruising down the street, this will be a very bad outcome. Please tell mary barra to keep her promise no more crap car. This problem is going to hurt someone.