Customer pricing of O365 plus support?

We have a few customers who are only getting A/V or Office 365 exchange online licenses and I am rethinking how to sell this. The problem is if they have an exchange online license for $5 a month and they need to reset their password or have a problem configuring Outlook they call us. Then the technician spends 15 to 30 minutes and we bill them for that time. They already paid for a year's license in advance but now we have to go back and bill them for 15 minutes or whatever. We often do very little work annually for these kinds of customers unless they have a project. One of our customers got sold exchange online for $7 a mailbox and they have 4 licenses. Its unclear what the terms of the contract are but I will be sending out a contract outlining what it includes. Say we get a license for $3.5 and charge $7 that's a $3.5 profit times that by 4 mailboxes and that gives us a profit of $168 annually. Ongoing maintenance of the O365 tenant is very little so I think we can offer 2 hours max annually for "support" Over the last year they have only called to add a license and they got a new desktop and could not configure Outlook themselves.

Yes I understand O365 is a loss leader but its a sticky service that keeps us engaged with a customer for other work. My question is on pricing and how to include a little support. How are you marking up O365 for these kind of clients?