Depends on what they did. If it was illegal and you've got proof, call the police. If it was a minor infraction that was more insulting/annoying/rude than anything else, contact management. If it was management, contact corporate. And as always, you can voice complaints on social media and either tag the location/company or post it to their page. But I seriously doubt any of this will get you anywhere. Unless they were just blatantly racist or attacked you in some way, your best bet is to take a deep breath, assume it was just the employee having a bad day or some other circumstance out of your control, and move on with your life.
Get there name and contact the local Walmart gemeral manager. If there is no responce escalate to the district. But remember people do have bad days and sometimes its easier to overlook once.
Thanks! Your answer is awaiting moderation.