What is the change? If it is a speed upgrade even that requires Openreach intervention. Try switching your Hub off for a full 30 minutes to allow the session to reset at the DSLAM and see if the speed improves. Otherwise, call NOW again if necessary to find out what's happening.
It would be helpful to know just what change you are hoping to make.
There are only 3 options on Now. BRILLIANT BROADBAND (ADSL only, up to approx 20Mbs), FAB FIBRE (up to approx 40Mbs) and SUPER FIBRE (up to 80Mbs).
The speed you will get depends on the quality of your Openreach line, you can check what they expect your line to be capable of here: