Fly in my house (Santa Clara County, California)
You may want to consider getting some fly paper. It is a sticky sheet that has an odor that attracts flies and they get stuck on when they land on it. Very efficient. 

There are also fly sticker products that are a strip of the extremely sticky material that pulls out of a small round paper canister. These come with either a loop on the end for hanging or an integrated thumb tack so you can hang them from the ceiling in the room where the flies are most apt to congregate.

Growing up on a mid-west dairy farm in the '60s it was a common problem to have flies in the farm house so there was almost always a fly sticker hanging from the light fixture in the center of the kitchen dining area. Once the flies land on the sticky paper they may buzz for a short time before they give up and succumb to their fate.