In the past, Spark charged $9.99 per month for "Ultra VDSL" on top of the price for ADSL. However, their current plans have ADSL and VDSL at the same price .
If you have changed to a current Spark VDSL plan (and are not on a fixed-term contract), you should be paying the current price (i.e. no $9.99 surcharge). Unfortunately it seems Spark may only stop charging the extra $9.99 if you contact them and ask.
This was the case for "kiwipearls"  and "Jase2985" . Both of these Geekzone members were paying the $9.99 surcharge - when they spoke to Spark about it, they were able to get the surcharge removed from their bills and obtain a refund of the surcharges paid since November 2016.
I too have contacted Spark to get the $9.99 surcharge removed from my bill. Unfortunately I was not able to get previously-paid surcharges refunded, but at least I will not be paying the surcharge from now on.
Make sure you are not paying an avoidable "Ultra VDSL" surcharge either.