Your question is an employment law question, not a criminal law one. I would first suggest you try reposting under that topic. Walmart no doubt has a set of employment guidelines or handbook that tells what you can be fired for and the employer's policies for those in your situtaiton. Request of a copy of it. It should outline your rights and steps you can take.
This information is for general information purposes only and does not create an attorney-client relationship.
Oklahoma is an at will employment state meaning that an employer may fire you as long as it isn't for an illegal reason like filing a comp case or discrimination. However, courts have interpreted employee handbooks and procedures potentially as an employment contract so look at it to see if they violated their own procedures.
Answers to AVVO questions are for general purposes only and do not establish an attorney-client relationship. This answer is not a substitute for legal advice and should not be relied upon without a full consultation with an attorney that can fully look at issues involved.