Exchange Str8 Talk Hot Spot Cards for Air Time Card

Please help me. An employee of Walmart picked out and sold me the wrong straight talk cards for my two phones I purchased instead of straight talk airtime I was sold and purchased straight talk mobile hotspot I cannot use these cards as they are inferior to the phone service that I need I paid $50 for each card Walmart told me that to get ahold of you for a refund or to exchange them please contact me as soon as possible so that I can start this process thank you so much look forward to talking or chatting with someone soon.