I don't think that would happen. Imaging is not exact so they may think it's one type when it could be another.
A simple cyst is fluid-filled and a complex cyst normally has some fluid and some solid components. Another characteristic of complex cysts is the presence of septations. Multiple simple cysts may appear to be one complex cyst on ultrasound as the borders of the cysts may be misinterpreted as septations of one larger cyst. I hope that makes sense.
How large is your cyst and when was it discovered? What has your doctor recommended?