Other posters report they have had success in forwarding these illegal texts to 7726. They are picked up by your cell phone carrier who will ask you to send them the phone number so they can investigate and have spam filters installed to block the texts. The following article tells you everything you need to know:

Security company Cloudmark created a spam messaging reporting service that nation’s major wireless carriers agreed earlier this year to start using. Now, customers of AT&T Mobility, Verizon Wireless, T-Mobile, Sprint and others can forward their text spam message to 7726. The mobile phone carrier will ask customers for the phone number that’s linked to the spam message so they and Cloudmark can start investigating.

http://www.ajc.com/news/business/text-spam-messages-on-the-rise/nSW3C/

Is what the sent:haha if you want to know who this is you got to add me on Y! messenger. my id is txtiegirly973

Got the text this evening saying hey <my name> and it was spelled correctly which is weird since I have an unusual name

Said hey Randi. But they got the wrong number. When I asked who it was they said I had to add them on Yahoo Messenger. Then I got another one today from a different number. These idiots don't realize that they have the wrong number. If I ever find out who they are I will be turning them in for harassment.

i got the same message saying hey _____. there spamming for emails. she did the same thing to me.. told me to add her on yahoo.