My process

I wonder if anyone can see any flaws in my plan or suggest better processes.
My directory on launch will have around 3000 basic listings on, all entered by admin. I will then write to each business inviting them to upgrade to silver or gold listing. To do so, they must first register an account, and then “claim their listing” which loads a contact form where they must use their registered email address.
Once received, I can change the owner of that listing to them.
One thing I have thought of is what can I put in to place to ensure the person who registers and claims the listing is actually from that business? There is nothing to stop a randomer registering and claiming 20 of the listings.
Any advice would be appreciated.