How do I sue Walmart for denying me service

I was denied service at a Walmart store, money transfer. The store clerk requested me that to give (not show) my ss card (the physical card) I offered unexpired state ID but she wanted SSN card, I explained to her that she cannot ask me for the card, I explained to her that i know my number and can tell it to her, but she insisted on the actual card. I insisted she call the store manager, but he behaved the same. He told me that it is the Moneygram policy to produce the SS card. I explained to him that his request is not stated anywhere and he should honor my request and render me service, but he threatened me to leave the store or he would call the police. Next step I called MoneyGram, and the customer sercive rep told me that yes per Moneygram that's perfectly fine with telling walmart the ssn and showing ID would work, but he suggested that I better take my business somewhere else, as some stores have their own policies. I asked again the manager to serve me...