Ah,
I do this everyday, i nfact one of the apps that I use is based on doing just this. It is quick and easy to use. I have had to change providers a lot so it is a simple thing to do. LEave me your e-mail address and I will send you the information. Takes about 10 minutes to load up and the rest is a cake walk. I Think it cost us about $100 and you can use it over and over. We have even changed it to work with pagers since Text messaging on Cells really sucks.