Most of the time this comes from signing your Mobile number up on online applications. Or if you ever send one TXT to any of those Late night TV ads.

You send one TXT and they will send you tons of messages. I have had verizon for three years and have only receied one TXT from any company. I did not respond and they never sent me another one.

If you have not ever sent a TXT to any of these companies or put your cell number on an online application then i don't know why you are recieving them.

Go to VText.com and sign up. It is free. Then go to text blocking and choose not to allow text messages from websites and e mail. I don't know exactly where yours are coming from but it should alleviate some of it.