Hello Rahul

Students are called for interview and the next rounds on the basis of their aggregate score which comprises of various factors such as CAT marks, 10th and 12th and graduation percentage, work experience, etc. 
Apart from the CAT scores, you need to have a strong profile to get a call from IIMs and since your class 12th scores are not good, you need to cover that loss from your high CAT percentile.
You need to score 98+ percentile to expect a call from IIM Calcutta

Hope for the best.
Good Luck!