I own a small gas bleed within a house we simply bought. Who fixes those? I tight, what would that being be call? Thought I'd try to find it in the phone book, but don't...

Thought I'd try to find it in the phone book, but don't know what to look lower than. Thanks for any help. Of course, the gas is turned OFF presently. The gas company was going to turn it on for us, but they found a seepage.