Would You Be Missed?
If you assigned your client to a new salesperson in a different organization, would you be missed?
If not immediately, when? At what point does your client realize that you are the secret sauce?
Don't settle for the "great service" answer. Identify what about your service sets you apart from everyone else. Once you've identified it, make it actionable and promote it.
Great service is now a cliché. What is it that makes you different?