3D/4D ultrasounds

Okay so I'm supposed to find the gender out sept 12 but I don't wanna wait that long so I was thinking of doing a 3D/4D ultra sound to determine gender. I was reading and some were saying the technician was wrong and said it was a boy when it was really a girl, vice versa. Has this happened to anyone?? I'm 15 weeks and 5 days, wanted to do it maybe next week. Did anyone else do it around this time and was it right?