Walmart complaint: refund

Yesterday I went to the Hayden Meadows Walmart store number 05899 and the employee helped me purchase a prepaid phone I was getting as a gift and the employee told me I had to also purchase the airtime card. I got home to activate the phone and the airtime card was not compatible with the phone. It turned out that I had to contact customer service and pay again for airtime. I went back to the store and spoke to the manager this morning at 10:30 am and they are refusing to refund the airtime card they said I had to buy and did not need and cannot use with the phone. I showed my receipt and advised the manager the employee said I had to buy the airtime card and it was not correct and to do the right thing and refund the employee mistake he would not and I contacted customer service as well and they refused to do anything I was transferred a few times and had to give up. This treatment is unethical and being that Walmart is a multibillion industry against my purchase power of 37000 a year does not compare. I am disgusted at this procedure. It seems Walmart is double dipping regular folks to make their billions. If I don’t get my 30.00 refund I am calling all the news outlets in my reach about this.