A strong managed IT support service should give you a clear service desk, defined response times, proactive maintenance, and real ownership of issues from start to finish.
You should expect monitoring, patching, vendor liaison, security basics, and regular reporting. If your provider only reacts when something breaks, you are paying for a helpdesk rather than a managed service.
The right MSP should also communicate clearly with non-technical stakeholders, document your environment properly, and help you plan improvements rather than just closing tickets.