The services OLA offers in Kolkata is so bad that it is pathetic, however I would like to share some of my experience, I have not been able to book an OLA CAB ever in one go, most of the times their driver say that they wont be able to reach even though in the app it shows that they are at 5-10 mins distance, sometimes they dont pick up the phone, in the morning time they never come how much you try.
I have totally stopped using OLA its lot better to use UBER or our own old Yellow Taxi. Never trust ola for catching flights and train make your arrangements beforehand.