I checked out your website, and your idea is interesting, though I wouldn't recommend it to anyone for the reasons I mentioned above. What works for other types of businesses may not work for insurance agents. I wouldn't put advertising money into branding a phone number I don't own. Agencies can do for themselves what you are offering by branding their agency through advertising. Vern Fonk is a big non-standard auto insurance agency where live. I see their ads on TV all the time. I have no idea what their phone number might be, but when I think of Vern Fonk, I think car insurance -- and really stupid TV skits.
Do you have testimonials from agents stating how your service increased their sales? For your service to make financial sense, it would need to increase after tax profits more than the cost of your service, increasing sales beyond any other phone number they can brand.
Some agents are always looking for the "one magic trick" which will increase sales and make selling easy. But there are no magic tricks -- just the hard work of getting out and meeting people, networking, establishing relationships, and figuring out what marketing is worth the cost and time.
I wish you luck, and hope you succeed in providing a worthwhile service to your clients.