Help Could Metro PCS have sold a phone with a used battery?

My mom and dad just got their first smart phones, the LG Optimus M.

Last night while my mother was at work, she had a battery life of 75% (battery widget). She surfed the web and listened to music for a half hour and it brought the battery down to emergency levels.

I know the battery life isn't the best, but this is unacceptable.
in 30 mins it went from 75% to 15%? I do know that metro wifi service is always updating your GPS location and used to drain my battery. Try and disable the GPS location services and see if that helps. It use to drain my battery down really fast too. Lmk