Switching from a normal British visa application to a premium service

I started my application on the vfs website to apply in New York. Regarding the payment, I see that it brought me into the processing centers with regular service option or priority. However, there was no immediate appointment.

I then went to the premium service website and I bought the Silver package referring to the application mentioned above. My question is: is the Premium Silver package a supplement in addition to the usual application fee? Will I still pay the visa fee on the application?

The process is a bit confusing and there seems to be no number to call. Please help.