You can upgrade your account at any time. It will take only few minutes. Just pay the price...I have already had a domain. Am I entitled for any discount, if I want to buy a web hosting?
No. Our price is fixed (with or without the domain registration), as we are giving away domain...Why No Unlimited Disc Space / Bandwidth?
You may refer this article for the answer : http://www.weluvpeace.com/blogs/viewstory/343