Hey guys: CS for a Services company is just as important as a product company, if not more: Service organizations often struggle to find a business model that includes that magical, “renewing subscription” so earning that next project and enthusiastic referral is even more key to long term growth.
If the service can be very clearly defined in a box (“productized”) then the basics of product-focused CS hold true. Think of the introductory “audit” or end-of-cycle “analysis” that has clear deliverables, known effort, quantifiable impact on the client, etc.
If the service is more customized, then I have always found success with the CSM acting as a hybrid PM / Analyst: Involved in the day-to-day but also part of setting strategy and reviewing impact. Happy to share more stories if that would be helpful.