Sorry about your bad day. Does your supervisor train staff regarding how to respond to difficult customers. In retail, the saying may go “the customer is always right”, but that is not always the case. In my present job I often speak to clients on the phone and some are angry at the organization and/or have known severe mental illness or trauma history. So as a result focus on calming them down and approach it as “I understand you are upset, and how can I help.” Sometimes it is just a really difficult situation to be able to help or convince them so have my supervisor speak to them.