Have you tried google? You can search for companies that will let you blast out text messages just like you would an email blast or newsletter. Text can be formatted like this.
"This is company we added you to our automated text message announcement… whatever
To stop recieving these text text back stop
If they don’t text back stop it is fine. As long as you don’t spam them and send out quartly emails it is cool. Its super effective too. This one fireworks store sends me texts every few months and even though I don’t need any I still want to go buy a bunch.