Hey there Overdrive,
I had the very same problem. And yes you can change the primary address. Well I could!!! I was getting over 200 junk mails a day!!! Mine was in the form "username" and a number ie
username6@ntlworld.com, I simply changed it to
username7@ntlworld.com. (not the real name guys!!!) No more junk, I guess everything to the old addy was getting bounced. But hey I could give a damn!!!! It worked. I may change it back to see how it goes, I did change about 4 months ago. So there ya go. It can be done!!!
Good Luck