09 automatic shifting issue

[aballormA]

Il press the gas and sometimes it will hard shift or the rpms will shoot up after i brake and it downshifts, like i will let go of the gas and it will stay up for several seconds before it falls. If i press the gas and let go quickly while it does this sometimes it fixs it. Not too sure what the issue is but my milage has been really shitty as well.... I just got a transmission flush (30,000 mile maintanance) and the car barley gets like 300 miles a tank.