Hi Deblina Gupta,
Firstly check if your variable is a customer exit variable & you have to hide it .
Also I_STEP is 1 or 2 ? Hope you know the difference.
Normally it should stop if the steps are followed. probably you might have missed any .
Please try to check again and also give details on how to debug ( 3.x / 7.0 )?
we can check further if not resolved.
Regards,
sudhir