Thought it might be a good idea to post the official Walmart Ad Match guarantee.  You can click on the link to read their entire coupon policy or read the ad match section following:

We’re committed to providing low prices every day. On everything. So if you find a lower advertised price on an identical product, tell us and we’ll match it. Right at the register.

We gladly match the price in the following types of ads:*

• Buy one, get one free ads with a specified price
  • Example: Buy one for $2.49, get one free (BOGO)
• Competitors’ ads that feature a specific item for a specified price.
• Preferred shopping card prices for specific items that are in a printed ad.
• For fresh produce and meat items when the price is offered in the same unit type (lb. for lb.; each for each)

*The following are guidelines and limitations:

• We will match any local competitor’s advertised price.
• We do not require customers to have the ad with them to honor a competitor’s ad.
• Items purchased must be identical to the ad (size, quantity, brand, flavor, color, etc.)

We DO NOT match the price in the following types of competitor ads:

• Items that require a separate purchase to get the ad price
  • example: “Buy [item A] to get [item B] for $C”
• Items with no actual price that require a purchase to get free product
  • example: “Buy both [items A & B] to get [item C] for free”
• Items that require a purchase to get a competitors’ gift card
  • example: “Buy [item A] to get a $B gift card
• Buy one, get one free (BOGO) ads with no actual price given
• Going out of business or closeout prices
• Percentage off
  • example: “All mascara, 40% off”
• Competitors’ private label price promotions

We do not honor:

• Ads when the actual price for items cannot be determined.
• Internet pricing
• Misprinted ad prices of other retailers
• “Going out of business” sales or “close out” prices

If you’ve been having problems with your Walmart following their own policies or experience ymmv situations, you might want to print out the pages from their site (using the link) and keeping it with you.