2007 GMC ACADIA User Comment / Complaint

I have had my transmission worked on already on my 2007 gmc acadia the speed control in the transmission has been replaced but i still have a problem with the performance of the car. it is an all wheel drive with an automatic. it will not hold on a hill and searches for a gear or chances several times when it comes to any kind of incline even at 70 mph.i was getting 15 miles to the gallon before the new speed control now i get 13. i have spoken to my dealer several times and he says to wait and soon there should be a update in the software to address this problem i am willing to wait but want it on record that the transmission has problems. this is a new design and is very rough riding. my car has only 5000 miles on it and i have been there 4 times.