I'm hoping someone may have some ideas on how I can handle this problem?

My client is offering a paid online subscription and after the person pays via clickbank, they are redirected to the registration page. This works fine for most part, however I have some people that have discovered the link to the registration page and keep registering "free" and hence getting members access. I have to then unregister them and delete their user account.

The system must be automated so I cannot manually approve the registration.

Any ideas how I can handle this issue?

Hey there...I have thought of a way to do this but still need some help. I was thinking that if I could have a code to add on the registration page that the customer has to add to verify their registration. The code would be set by me, and the customer would have to have the code correct for the registration to be successful.

Any ideas or extensions that could achieve this?