In ISO 13485:2016 in section 1 Scope is stated that this standard can be equally applicable for both medical device production and related services. This means that instead of production you will describe how you provide your service. Of course, certain documented requirements want to be applicable to you. For example, if you do not provide sterilization process, then requirements (and all applicable documentation) 7.5.5 Particular requirements for sterile medical devices and 7.5.7 Particular requirements for validation of processes for sterilization and sterile barrier systems are not applicable to you. Also, if you have no implantable requirements, then requirement 18.104.22.168 Particular requirements for implantable medical devices is also not applicable to you.
You have to state all requirements that are not applicable and write a justification for them in the Quality manual.
For more information structuring ISO 13485 Quality Management System, please see the following article: