text message spam on prepaid phone

I'm getting text message spam on my prepaid phone.
The first line of the message says it comes from AOL IM, from an ID that
looks like random string

I just called tmobile support and the person answering the phone does not
seem to understand text message can originate from email/IM. He said to send
the message "stop" to the caller. I'm pretty sure if I IM the AOL id that
spammed me, I would not get a response or may even be upgraded to the
"confirmed phone#" spam list.

I asked if I can disable the text message feature and the answer is no,
because prepaid refill info is sent to the phone via text message. Can't
they add a filter so that only tmobile can send me text message? I can live
without seeing the refill info on my phone because I can check them on the
web.

Another solution offered is to change my phone#. This is not acceptable
because it's a vanity number that I own for many years.

Has anyone been able to get tmobile to either disable text messaging
entirely, or delete the IM/email to phone feature?

If I get a gsm phone without text message feature (does it exits?), or a
phone that can turn off text message, would the phone relay this to the
cellphone station, and cause it to automatically disable sending text
message as well?

I hate to think that pretty soon, spam would cost me more than my real phone
calls.