| | Maybe not tech
You're going to resist this, but it's the most effective and least expensive avenue, though not the fastest.
File a police report.
You're dealing with a theft of service. If you're paying for those messages and air minutes, you're also dealing with theft. If the originator is out of state and it happens more than three times, it may even fall under the RICO (racketeering influenced corrupt organization) laws. While your instance may seem like petty theft, a mesaging spammer is committing compounding any crime through volume.
You can trace the source of any phone call or text message - or if you can't, your carrier certainly can - and they are much more likely to cooperate with a police investigation than with a call from you.
And unless this bad guy is severely self-restrained, the odds are it will get sent to the FBI.
You may have invited it.
You may have opted into getting these messages when you signed up for something "free".
If you're absolutely sure that isn't the case, file a police report.
They're open now, and if you like, they can deliver.