I have taken the services of the C&K though IVR for a trip to Sikkim. Initially they provided us the schedule for 8 Nights and 9 days. Once we agreed on the cost and paid the sum of 40K. They said that due to some political issue a site can not be visited and hence the journey needs to be planned for 5 nights and 6 days. They did not reduce the tour cost proportionally.
I have had better experience with Travel Planners. Unfortunately they operate only in Kerala and Andaman/ Nicobar.
Cons with CNK:
No single point of contact. Every time you will have to call centralized help desk and deal different customer care executive.
Turn around time in case you have a query or requested for change in plan is 24 hours.
You are just an ordinary customer for them.
Itinerary is not customized as per age group. Even if you are young and ready to do any adventurous activity, they will plan for routine visits to temples.
Unreasonably overpriced.
Stay is ordinary.
If possible plan on your own but avoid these folks.