fixing domain/url on my mystile wootheme

Hello,
I have set up a word press site with bluehost. At the beginning i used the default domain they provide. I purchased a domain with another provider and set the servers to wordpress, that worked fine. When, I load the site, https://www.piperandpresentcompany.com, it works fine, then I click on the posts page and it reverts back to the default url, same happens when I click home again. The about us and contact us page are fine. I contacted bluehost who said it was a problem with the mystile wootheme I was using, so they changed the theme and it worked but I want to use the mystile woohoo them, can anyone work out how to fix this please?
Thanks