2016 Toyota Corolla - RPM kicks up

we took the 2016 corrolla into the dealership for a 2yr service check at the same time they did a software update. about a mo later the RPM would kick up to 5000 RPM w/no acceleration
this would happen quite often. from a dead stop you can accelerate and the RPM would kick up and no speed took the vehicle back to the dealership 3 times they say they can’t duplicate it. even got corporate involved to no avail. also because the vehicle is always running at a high RPM the gas milage has dropped about 11 MPG. we also asked the dealership to put the software back to what it was since we didn’t have a problem before they said they can’t do that. any suggestions. thanx

Are you saying the rpms jump up but the car doesn’t speed up? That sounds like a transmission problem. And happening a month later makes me doubt it’s the update causing it. Can you not duplicate it?