I booked a cab last October in Kolkata for a trip in the city for visiting Durga idol/pandal and lighting.I booked that 1 day prior to the tour for 6-7 hours only.They readily accepted and told me the rate.Over phone we chalked out our plans.I selected as I had thought it would give us service without hazards.
On the day we were ready and the taxi did not arrive and after 1/2 an hour while I called they said it would take 2-3 hours more as it was busy ferrying other passengers/tourists during Durga Puja.If they had told us I would have hired a local car and it would have been cheaper.I cancelled the booking and quite late at a time when Kolkata is the most crowded city all over the world, left for darshan. That;s why I would never book a cab from their organization.
I would recommend that if you want to book a cab you can keep your finger crossed that they would give you some excuse.Otherwise directly go and pick up a taxi plying on the road, interact with the driver, bargain and come to a rate and take service.Otherwise it will waste your time specially it will be dangerous if you have to go to railway station or airport.Be careful.