Is there a way to hide the kaseya service? I have already been renaming it but I have a customer who will just stop any service he want to.
No... at least not easily or legitimately. Think about it... what you're asking for is basically malware.
Your problem is the user has local admin privileges. Try to get rid of that first.
If you can't strip their privileges for whatever reason, give the attached script a shot. You will need to plug in your unique Kaseya ID where applicable. The script will cause the Stop button to be grayed out. However, any administrator can still end AgentMon.exe. To work around that, we can force the service to restart itself automatically. The process will be assigned a new PID, but the agent will never go offline (in theory).
I will also attach the "Undo" script.