Transmission hesitation and failure

So, I'm really confused. Since I bought the car 6 months ago, the transmission has often hesitated changing gears. When it gets hot, frequently it doesn't shift properly and the car lurches when the car drops forcefully into gear. Now, sometimes the car stops changing gears altogether; I get stuck in 3rd or 4th gear no matter how much gas or torque provided. I just had the transmission fluid changed, so I doubt that could be the problem.

Ideas?
William
'97 Ford Escort LX 110,500 Miles

Did it start acting this way before or after you changed the transmission fluid? Some cars don't like it when the fluid is changed if it hasn't been changed before and the transmission tries to fail. Good luck though!

The engine has shifted hard all along, but it only started failing to shift after I changed the fluid. Today, I had the service tech check the levels, so the fluid levels are correct and look good.