Walmart's policy is simple. follow state law. Associates including managers do not have the discretion to modify or ignore policy. Call the store manager first, name should be on the receipt. If he doesn't resolve the situation, obtain the name and number of the Market Manager...his /her name should be posted at the front of the store or in the back by the Site 2 Store area. Last but not least, if that doesn't work call the corporate number and explain that you have already talked to the store and market managers. This will get your call elevated.
Don't call the corporate number first because all they do is send it to the store to resolve. The store manager should be able to resolve the situation as they don't want anything going to their boss the market manager.
I worked as a manager at Walmart for five years. This is the best process to follow to resolve your issue.