TheRegnirps 
I have been having a terrible time getting a SIM in the US for GSM SMS and that will work with a Wavecom or a Kingbird quad band MODEM. AT&T pay-as-you-go cards require a phone serial number under contract (or some similar problem). T-Mobile will not attach to tower. Virgin Mobile is CDMA. I'm using Python and pyserial to send AT commands and also just Minicom to test by typing in a terminal. Any success stories out there?