"but I want to tell them why they need to switch."
Why not focus on the ones that already want to switch but don't know how easy it is? This sounds like a reconnaissance challenge. You need to know who's providing what to what and who sucks at it.
So one way is networking ... you get your people to meet these customers and act as a customer - you're a startup looking for IT, can you recommend anyone.
Find out the biggest complaint (I think it's highly likely about response time - 99% of the time they call it's an emergency to them so unless someone answers in three rings, even at 2 am, they don't like it)
Then you approach these customers with an essay, video essay would be best, telling them first hand that IT is kinda worthless when you're not confident you can't reach who you need, when you need and you want to give your customers a 'three ring response' time so good that Zappos would be jealous.
I can personally tell you how critical time is and I'm only a web designer. When I get an email inquiry I literally reply in about 30 seconds and if they comment about that I even apologize, jokingly, that I took so long to reply. Most every time, unless we're just not a fit, that's a new customer.