Blogger are writers. Perforce they are capable of comprehending and following written instructions with a little help from friends. You want to map an existing domain (one you already own) to your WordPress.com blog and there are written instructions for that. Follow these instructions if you already have a domain that you registered elsewhere, and you want to map that domain to your blog. http://support.wordpress.com/domain-mapping/map-existing-domain/
P.S. There is no phone support here. If you have purchased an upgrade then you can contact Staff directly using this link http://en.support.wordpress.com/contact/ If you have not purchased an upgrade then simply post what you need help with into a forum thread.
This is a peer support forum where Volunteers and Staff work cooperatively to deliver WordPress.com support. Volunteers answer most questions and Staff monitor. When Volunteers cannot provide the required support we flag threads for Staff attention.