Ben has definitely hit the nail on the head with his reply.
As someone with two VAs in my team, I've been contacted by various VA agencies that couldn't explain their business model and what differentiates themselves from others.
Do your due diligence and figure out what makes you different and better. With Zirtual as an example - would you offer VAs in more countries in order to help other markets? Are your rates more affordable then theirs? Is your selection process more refined?
Based on your access to VAs, structure your brand message and define your perfect customer. Do some customer development and jump on a call (or email) with some prospects, and see what sort of help do they need and how can a startup like yours help them.
Shape your strategy in a way that corresponds to their needs, and align your pricing to your audience. Then all of your marketing can be focused on that group of people and your conversion rate would be much higher.
Happy to provide some feedback as someone who's hired VAs before.