Applying for a visa is no simple task, it cab be very complicated. You need to make sure that you are using the correct form. The forms change from month to month so there is a real possibility that you may have used the wrong form.
The visa application charges are also subject to change. If you pay the wrong fee, then you may have made an invalid application and you may not be granted a visa. The visa application charges are very high. If you apply for a visa and the application is refused, there is no refund of your visa application charge.