A company that provides only technical service has to prepare the ISO 13485 quality management system as follows:
First of all, your „medical device“ is technical services and technical writing. So, everywhere in the standard where it is written medical device, this is your service.
Second, requirement 7.5 Production and service provision, for you is only Service provision. Accordingly, the following requirements probably are not applicable for you: 7.5.5 Particular requirements for sterile medical devices, 7.5.7 Particular requirements for validation of processes for sterilization and sterile barrier system. If you are not providing installation of equipment, then requirement 7.5.3 Installation activities are also not applicable for you. If your technical service does not require specific cleanliness conditions, then requirement 6.4.2 Contamination control and 7.5.2 Cleanliness of product, are also not applicable for you.
For more information on ISO 13485, please see the following articles: