Have gotten a text from this one twice in three days - in Spanish, yet.  The latest one reads:

"Su giro termina en 4972 ha sido recogido el dia Mar 25 2015 8:36PM Gracias por usar Intermex.  Envie STOP para cancelar notificaciones."

Google Translate says:
"Your turn ends in 4972 has been picked the day Mar 25 2015 8:36 PM Thank you for using Intermex. Send STOP to cancel notifications."

I'm working on the assumption that sending STOP hands your phone number over to somebody who will do bad things with it.  Number ID's to Florida - Fort Lauderdale area.  Intermex is a genuine company that handles money remittances to Latin America, but their contact number is in Miami, with a 305 area code.

How can i stop them or block them from using my phone number?

I recieved a nearly identical text to the one MikeK got.

I have notified the company Intermex and will update once I hear back.

Did you ever figure out where these texts were coming from? I have gotten the same one!

received = su giro que termina en 6838 ha sido recogido el dia 01/06/2016 at 12:14pm
WHAT!!! - I HAVE NEVER USED INTERMEX - scam!!