changing broadband package confusion - help needed to understand.

[#1]

Hello
I would like to change my package from :
PlusNet Broadband Premier Option 2 (Annual Contract, No Modem)
To
Plusnet Unlimited (No Contract)
But it says my download speed will be limited to 8Mb if changing, yet if I was to signup with a brand new plusnet unlimited account I would get upto 16Mb (I am on adsl2)
e.g :
Unlimited Broadband features
    Up to 16Mb speeds†
    Just click 'start your order' for an estimate of the speed you can get. We'll just check your phone line, there's no commitment to buy anything.
Is there anyway of changing my package to the unlimited broadband without cancelling and starting all over again?
thanks

[#2]

I know getting that estimate is unsettling but upgrading your package to Unlimited will have no effect on your current speeds. Due to a bug in the system the estimate provided is for ADSL1 (up to 7.6Mbps) and not ADSL2+ (up to 16Mbps) as it should be in your case.
To order the upgrade just do it through the Member Centre and ignore that estimate. The upgrade will be applied on your next billing date. Until then all you will see is a closed service notice on your account detailing the change.