Who called from 4086378161

I've rec'd two of these in the last two days and I don't give out my cell.

I, like the others on this site, have received several texts from the number 408-637-8161, all saying to reply for a Wal-Mart gift card of $100.  When i tried to reply stop, the number didn't work.  How do I make it stop?

I also received this text message, "Thanks 4 visiting Our Website Please call 877-861-8581 to Claim Your $100 Walmart Gift Card.  I suspected it was some sort of scam.  I did not call the number.