2001 can't decide on a gear

We also have a 2001 Cavalier that I rarely drive (my wife does) and I recently noticed that when going up hills, especially ~40mph, the autro transmission can't seem to decide on a gear. It will continually shift between 2nd and 3rd unless you give it a little gas to force it into 2nd. Does anyone else have this problem? It seems like something a simple software/firmware upgrade could take care of. Is that possible?