Written into the contract before delivery begins. CN returns and verifies that the change held and the benefits are being realised.
The person in the pitch is the person on day one. No handoff to a delivery team you have not met.
No technology platform to sell. No audit practice. CN's only interest is that the work delivers what it is supposed to deliver.
Tell us what you are dealing with. We will tell you honestly which service applies — or whether it is a combination.