Error with unpaid invoice

What is the name of the domain?

mediomaratonbenidorm.com

What is the issue you’re encountering

I want to add this domain under free plan in cloudflare, but I get an error “You cannot add or modify subscriptions or services until the outstanding balance is paid. You should be able to do so in your Billing page.” . How can I fix this? It must be the debt of the old owner?

Screenshot of the error

You’ll need to follow these directions here, Billing, Plans & Subscription Questions