Your Webstix Service Agreement should specify how many pages we've estimated your website will need. We often include a number of pages in our basic CMS package and then charge an amount per page for additional pages.
As the website is designed and copy is worked on, it's common for more pages to be added. When that happens, you have a few options:
If you do want us to add in content and do layout for extra pages, then just let us know. We'll adjust the final invoice to reflect the additional cost.