This was highly non-obvious to me a few years ago, so I'll mention it now: Customer expectations for most B2B applications frequently do not include being able to pick up a phone and talk to someone during business hours. It surprised me, too. I offer "24 hour response times, best effort, via email only" as the standard plan for Appointment Reminder and get very, very little pushback. When it does happen, I quote a $5,000 a month SLA for call-me-any-hour-day-or-night phone support. I don't sell any of those, so it's been a wild success. (If I ever sell one I'll dry my tears on the money then quintuple the price for the second customer.)