Random post I found...
CHANGING ORIGIN USERNAME USING iPhone
"I was reading on the EA UK Battlefield 3 forums and someone posted about changing your Origin ID, and to my surprise it actually worked. Here’s how to do it, requires that you have an iPhone or Android phone.
You have to install EA’s “Scrabble Free” app from the market. Once installed you can go to Options (The cog looking icon at the bottom), Click Log in to the right (use Origin email and password), then you can go back to the Options screen and clcik “Edit Account” and enter your new ID to get the Save button to work I had to enter my password for the New password fields, idk why."