I see. VoIP seems to be something I could support, but I know they are systems integrated with POTS in some cases, so if I support VoIP then it seems I would have to know a bit about how the POTS runs through the building.
I know I'm not going to be able to provide every single service out there, but if I can know a little bit about the service I can't provide I can avoid loosing money to outsourcing, so when finishing writing my service agreement, I have to decide whether I want them to come to me for everything, and handle the outsourcing for them, or have them handle all the stuff I don't do, by themselves. The former seems the better choice because you don't want techs coming in messing up what you've done on their network without some of your intervention, and it would make the client seem like you care more if you are involved more. Then again, if I've got them committed to so many hours per month, while outsourcing I might have to take a loss and use some of that money they gave me to another company for stuff I don't do.
Maybe I could have my clients who are under a service agreement contact me for everything and just figure out a way to minimize the profit loss for the outsourcing while having the third party company bill me instead of my client.