I'm a business owner who does some advertising on Craig's list.
The guy who owns this number has been spamming me with his number for MONTHS. I have told him repeatedly that I would not be willing to take him as a client (he thinks I'm a sex worker), but he keeps asking if I'd be willing to "do" him & his female roommate. He's been messaging me daily since early January with his phone number attached.

Do not respond to unwanted texts or emails from questionable sources. Several mobile service providers will allow you to report unwanted spam texts by simply texting/forwarding it to 7726 (or “spam”) to enable the providers to prevent future unwanted texts from the specific sender.

Source:
http://www.fcc.gov/guides/spam-unwanted-text-messages-and-email

More info:
http://en.wikipedia.org/wiki/Mobile_phone_spam
http://blog.usa.gov/post/89152807112/protect-yourself-from-text-message-spam

However, in many cases, the text origin, as seen on your phone, is faked.  The internet domain does not exist, or the phone number may have been spoofed.

Pretty sure you misread my post...

You said somebody was messaging you: " He's been messaging me daily ".
My reply suggested how to stop text and email messages.

Why do you think I misread your complaint?

Yeah, I've got the same complaint. Repeated messages for months. This guy has been filling my inbox with repeated messages about wanting my services, but when he's told no, he refuses to accept it as an answer.
He also uses the name "Leo Cortez" in his e-mails, but now he's using the same e-mail address, trying to say his name is George. If that alone isn't a red flag, even without the refusal to respect my boundaries, then I don't know what is.