Take down domain name without access

I'm currently developing a website for my client and she had an old website that she created through "clickasite.com". Since then "clickasite" has apparently closed down. However, weirdly enough they are still running her website. My client is still getting calls and enquiries from this website which she hasn't had access too in over 2 years now. Any idea how I can go about taking this site down? Thanks for your help