Here in the Las Vegas area the local natural gas company is Southwest Gas.

Their Las Vegas office is located at:
4300 West Tropicana Avenue
P.O. Box 98512
Las Vegas, NV 89193-8512

Customer Service Phone Number:
(702) 365-1555

Emergency Number (if you smell gas) 1-800-447-5422

You can request service online at the following link:
http://www.swgas.com/snv/forms/index.html

The following link will take you to Southwest Gas' Web Site.
Southwest Gas