could you link your module vendor page?
the sim900 indeed works with 3.3V but barely no one works with it directly, but most people get a small development board that includes the SIM900, a 3.3V Regulator, a SIM socket and an antenna, you need to check if your board includes 3.3v to 5V data converter for tx & rx.
it's very easy to work with it if you have experience with modems and terminal commands (AT commands) and there are a lot of examples on the web...
about your carriers, I know that the sim900 is quad-band that makes it friendly with most operators on GSM around the world, check that your operators work with any of 850, 900, 1800 or 1900 MHz on 2G. If your carrier operates exclusively on 3G or LTE, then this module will not work.