This is a scam. The caller is NOT Apple or Walmart. We are seeing a lot of these coming out of NY phone numbers today. Repeat: This is a scam. Do not respond in any way. Simply delete the message. At least some of these messages are directing people to a malicious site. Do not let curiosity get the best of you.
I just got my iPhone last week. Couple days later, I got the spam text message from 347-244-6781. That was quick! Someone has my phone number already. I am not happy about Apple on sharing my information to others without my acknowledge.