Sawing on the pipe will create the spark necessary to blow yourself, your family, and your house to smithereens (or to Texas). Messing with gas pipe requires a gasfitters license which most plumbers have.
I'm with Henry, get a plumber. Just in the way you asked the question, indicates to me that you probably lack the knowledge to try this on your own. It has to be shut off and capped in the right place and any pipefitting needs to be tested for gas leaks or else a slow leak may fill up your basement or crawlspace and ka-boom, you still end up in Texas. Good luck and live long.