There are a lot of professionals that have access to built-in vacuum system materials and offer repair services. Professional electricians, plumbers etcetera are highly experienced in their respective trades. Just as often, they have limited experience with central cleaning systems. Nothing wrong with that, but for the same reason you might not have your dentist fill out your tax forms, hiring a specialist that only works on central cleaning systems will likely be your best value.
If you have been told that these systems are very simple, you were told the truth. However, certain things done wrong can really mess up an install or a service call.
For example, a plumber will have PVC glue on his truck. It just happens to be the wrong kind. Any vacuum joints glued with Schedule 40 glue will likely come apart in about ten years. If this happens in an attic or open basement, no big issue. Inside a wall or above a dry-walled ceiling, big issue. Not to pick on plumbers here, but they are often trained to use a “fish” to clear a drain which is about the last thing you want to try with a clog in a centralized cleaning system.
Find the full-time vacuum specialist in your area before scheduling that service call.