I picked this up somewhere on the internet and it sounds just too good to be true.
I am a Linux newbie and could not get it to work, but maybe some magician out there can make it work. This example is for the AT&T network in the USA.
At the command line type:
mail -s "converged" (your telephone number) @ txt.att.net
do not enter the ( ) , just the phone number.
Good luck and be sure to let us know if this can be made to work.