How do I stop my Booking.com account registration process?

I now seem to have two logins with the same email address - one which is up and running. The main property has a 9.6 rating and all is going smoothly as far as I can tell. While getting to grips with Booking.com I started a new account registration and used my home address to get things off the ground... I then abandoned the process, but Booking.com is still sending me emails to get me to complete the registration process and has even sent me a verification letter in the post to my home. I cannot see ANY way to stop the inboarding and because I used the same email address that is now on the live account, I am having trouble deciding what in my Inbox is actionable and what isn't.