How to set custom domain

i want to apply for your premium service but i want to know if i can use my office name without www.joform.com appearance in it? because i need my form to have my office website attached to the from id

Yes, you can set your own custom domain. For more information please read this article:

http://www.jotform.com/help/144-How-to-use-Custom-Domains-with-Jotform

Hope this will help. Let us know if you need further assistance.