I started getting massive amounts of text messages from OZMAIL as well, and after looking for the answer everywhere on the internet, I finally fixed the problem using the following combination:
I sent an email to every email account I had until I found the one that would trigger the text to come up on my phone.
The account that was affected was hotmail, so I went to my inbox, clicked on "options" in the top right corner, clicked on more options, then clicked on the last option under "Reading Mail" called "Mobile alerts for new messages." At first I overlooked this because it wasn't enabled, but then I read on another forum and was informed by someone that you have to sign up for it, then go back under the preferences and disable it (to do that, I had to click on "sign up for windows live mobile" again in order to bring up the options for it, then you can find "Set up Alerts preferences").
After doing this, I sent another email to myself on that account, and voila - no more OZMAIL text messages.
I hope this helps someone!!!
All I did is respond "STOP" and "PLEASE STOP" everytime they send me the message and delete some of my APS on my phone that I haven't use for a while, and now I don't get the message anymore!!