If you are unhappy for whatever reason with your purchase from Walmart, you should have a read of their returns policy before shipping your items back, as returns policies are subject to change.
How to return an item to Walmart?
If you wish to return your item to Walmart using mail, click on 'My Account' > 'Track Orders' > 'View Details' - then click 'Start a Return' and from here you will able to obtain a free return label.
Then simply package the item in the original packaging and mail as per the instructions on the site. If you need some further advice on packaging your items you can learn more here.
Once the item has been processed by Walmart at their returns facility a refund will be issued. You can also return items purchased online instore as long as you have the original packaging.