15 week scan:)

Lisa
I'm 15 weeks and had an elective gender scan at a 4d studio. I have been told scans can be wrong:) I have a girl and they told me girl at 20 weeks with her. The tech said she was 100% sure, but I am just wondering... Has anyone ever been told boy and it was a girl? I have heard of techs being wrong when they said girl, but it was a boy...what do you guys think?