I've just signed up with plusnet. If a company offers a way out of a contract, it would be rude not to take it 
Did you get notification of the increase or did you just ring up? Which department you speak to?
I haven't had formal notification. I rang the generic "cancel some service" number and the lady was a bit useless. I rang but gave up.
From a landline: 0800 345 7310
I then tried to request a MAC via 0800 328 6738. I explained that I had seen the press reports of the price increase and wanted to confirm that it meant I did not need to honour my minimum term. He confirmed this and after a few minutes he gave me my MAC.
If you can't get your MAC today (I think they are closed) it's worth signing up via quidco anyway as their Plusnet offers expire today and the plusnet site allows you to provide the MAC after sign up.
Kris
BT Infinity 2 but migrating to Plusnet
Ashington (Northumberland) Exchange