Assigning Post Levels with a Free Account on Pro Sites

Hello

At http://www.messagewall.co.uk

I would like any user to have a free account with 3 posts and 50MB storage.

If they want 10 posts and 100 MB storage that would be BASIC.
If they want 10 posts and 200 MB storage that would be PREMIUM.

I thought I had set this up, but when you sign up for the free account, the message tells you in the dashboard that to upgrade you have to upgrade to the FREE account.

Please can you take a look?

I have enabled Support in my dashboard.

Thank you
Marc