This pop-up notification will only be visible if the email address you have registered is not associated with a screening interview (an interview that you've been invited to complete by a hiring company).
To stop the upselling page, you will have to sign up for Shortlist.Me interviews using the same email address as the screening interview (see your invitation email).
If you have not been invited to a screening interview then you'll need to pay in order to complete the PRACTICE INTERVIEW.