I have been getting a lot of text spam lately and thought I look into my options. Spam is just one of those very annoying things no matter how you get it.
There are two things you can do...
1: block whatever number is sending the texts. I have been doing this a lot as I was also getting random calls in the middle of the night. So this works but you just have to keep adding the number there.
2. I got from the article below which is a bit old but still works just the same now in 2017. You can forward the text to 7726 which is for spam. This let's the carrier know that that is a spam text. I just sent the spam text I got and this still seems to work.
Are these perfect, no but at least they won't annoy you as much. Spam is bad enough, but now getting that on your phone is just beyond bad.