You CANNOT automatically delete your Walmart.com account.
Try to contact them using this link to complain about this: http://www.walmart.com/cservice/cu_comments_online.gsp?cu_heading=8
You can also try to contact them by phone:
1-800-966-6546 (8am to 10pm)
How to directly reach a live person: Dial 238 as soon as the automated greeting begins (no need to wait for the menu options)