When the car is started and then shi...

When the car is started and then shifted into drive you can feel it engage. It will move forward and even seems to shift properly until the transmission warms up. Once it warms up and you stop it will not move forward after it is put into drive. If you do get it to move forward it will not shift out of first gear no matter how fast you go or how slow. I changed the transmission fluid and filter and it seemed to work fine and shift properly for probably less then 20 miles then it reverted back to the problem I explained above.