Wrong gender at 16 weeks?

Hi ladies! I was told at 16 weeks that I was having a girl but I recently saw a woman post that she was told girl at 16 weeks and boy at 20 weeks! Just wondering if this has happened to anyone?? Now my brain is going crazy haha. If this did happen to you - did they guess girl at 16 weeks or did they act confident? Did you see girl on the ultrasound?