Best Buy Overtime Policy Crap

My friend works at best buy in installs. He is a very hard worker and often picks up many extra hour trying to cover other employees. Last time (months ago) he ended up with overtime from getting overbooked with jobs he got in major trouble with his boss. He was worried about loosing his job over this, so ever since then he just hasn't been reporting overtime. He was been working equally as hard, just working off the clock to make sure he doesn't get overtime. Is there anything that can be done?