WordPress page url is being suffixed with -2

Hi all,
i have just noticed that my wordpress website is suffixing -2 on a couple of my pages. i think it is because i have created a page with the same name before but deleted it. i was wondering how i change this to just show about-us instead of about-us-2. the url on the edit page bit still show about-us so not able to change it there. im using the formations theme to.
Many thanks
Billy