Change Plans

Hi

How exactly do I go about changing plans on the slingshot website? I currently have 100/20 with landline for $100.95 but don't need the landline anymore. When I remove it from the website, the price only comes down to $94.95 while on the home page I see the price is $84.95.

Under my account I am seeing this alternative pricing:

https://www.slingshot.co.nz/assets/files/SS-Fibre_100-20-Naked-alt.pdf?v0.10.21

And when I am not logged in I see:

https://www.slingshot.co.nz/assets/files/SS-Fibre_100-20-Naked.pdf?v0.10.21

Is it not possible to upgrade to these new plans?

And the other question is regarding wiring insurance. The website says its recommended but the help page only mentions it covering broadband and phone line so is it actually needed for a fibre connections?

Thanks