I have a goodman furnace. My furnace is going on but the flame turns on and off frequently without the room temperature reaching the appropriate thermostat temperature. I have cleaned the duct,change the filter as per servicemen and yet I still have the problem. Any suggestions as to what I can check or do before calling a serviceman again.

What kind of pilot does your furnace have. You say the flame turns off before the thermostat is satisfied. How long does it stay off before it lights again.?
Answer some questions and it will be easier to tell you what might be wrong

Model #? Efficiency? Age? Does the fan run the whole time and just the burners cycle on and off?

Sounds like a defective limit control.