did anyone else find out the gender at 15 weeks?

I'll be 15 weeks exactly next week when I go to find out the gender. I'm going to this special ultrasound place that does 3D and 4D and HD etc. not my doc office. As it's getting closer, I'm getting so nervous that the baby will be hiding the goods and we won't find out and I'll have to cancel the gender reveal party which is two days later. My sister found out at 15 weeks but everyone else I know goes at like 18-20 weeks. I really hope I don't leave disappointed, especially after paying $60 to go to this place... if they're not able to determine the gender, would it be wrong to ask to reschedule without having to pay for the next appointment? Since this is the EARLY GENDER PACKAGE I'm getting and it says between 15-20 weeks and I'll be 15 weeks, so if they're not able to find it then I should be able to come back the next week or so, right? Without having to pay another $60? I just don't want to waste the money. The place says 15 weeks, I just hope they really do have success at 15 weeks.