redatm on "Changing .wordpress domain name"

Hello,

When signing up for wordpress, you get to chose a domain name.
For example, my blogs domain name is the following:
http://ridunkulousexperiences.wordpress.com/

My problem: Since I chose the domain name many moons ago, I have changed the name of the blog. I understand I can buy a domain name for an additional fee, but is there any way I can change the domain name of the blog to another .wordpress url?

For example, is there some way I could change my blogs url to the following:
http://kainiindustries.wordpress.com/

Is this possible?

Thanks,

Alex