Companies like these work as an agregetor and hires contactors,architects to get your stuff done and there is no option of going back once the plans are finalized. Also there might be cost over-runs and quality of work issue (Second hand experience as One friends work was ruined).
Again there is someone who is very happy with their work and didn't had any problems and give a good feedback (My Neighbours Sister).
Both this happened in different cities so I would suggest you get in touch with an Interior designer check there previous works and some references/Recommendation before you go forward.
Companies have set design palates but a good interior is like an artist who can bring your dreams through his creativity to life.
So which city are you planning to do this ?