Upgrading from Snow Leopard (OS 10.6.8) to El Capitan

I have a catch 22 situation. I want to upgrade from Snow Leopard (OS 10.6.8) to El Capitan (OS 10.10) on my 5.2 white Macbook. On the Mac store I can see El Capitan (see attached screenshot), but when I try to download it I get a 'Verification required' notice asking me to update my billing info. When I click the Billing Info button, I get "Software Update Required' which is exactly what I am trying to do. So basically I can't upgrade my OS to Yosemite without upgrading my OS. Grrr!

Any ideas?

ps: Oddly on the App Store on my OS 10.12.6 Macbook Pro, I can't find the El Capitan installer...