I just got one too from the same number. Assuming it's scam, since the full website isn't just www.walmart.com but adds .myfreecard.biz afterwards, which would means it isn't on Walmart's servers.
Got a spam text from this number, and I do not even have a text messaging plan - nor do more than ten people (all either very close friends or relatives) know my number. The link is very shady, for the same reasons Nathan stated, so I refuse to even attempt to view the website. I wish there was an easy way to block this sort of thing; it will end up coming out of my pocket because I do not text.