Freeview is the name of the (BBC-backed) digital TV system that uses hilltop transmitters to rooftop aerials. It is run separately from the "Sky" satellite-to-dish service.
free-to-VIEW is a term for satellitechannels that need a viewing card to watch, but not to collect a subscription. free-to-AIR channels are ones that can be received without needing a viewing card or subscription.
The free-to-AIR satelite service backed by the BBC and ITV is called Freesat. The free-to-VIEW service operated by Sky is called fSfS or Freesat from Sky.
As long as you have finished your first year, you can leave Sky when you want.
To do this just give Sky a call and tell them you don't want to subscribe any more.
You will still need to keep your Sky viewing card. If you stop subscribing on a Sky contract, you can keep using that card to watch 5USA, 5* and PICK TV, the so-called "free-to-view" channels. (All ITV channels are free-to-air).
It is not possible to plug an aerial into a Sky Digibox to receive Freeview channels because the boxes have not been designed this way.
You will continue to get the full Sky EPG listings; you just will not be able to watch subscription channels.
Mrs Sandra hawkins: Try placing the box in standby for 15 secs or so before disconnecting it from the mains, then whilst its in that state swap the two screwed connectors over, that is "if" you are referring to LNB1 & LNB2?
Finally, reconnect the box into the mains supply and allow it to go through its usual set up procedure, which by the way, can take a few minutes to complete.
A dish only receives signals from the satellite it is aimed at, in your case that would the ones used for Freesat and Sky. Freeview is quite different as it is transmitted using ground-based masts, so you cannot use a satellite dish to get Freeview transmissions, you would need a traditional aerial to get Freeview.
You should discuss your options with BT directly and they can advise how you can receive their services. I am aware that if you use BT as your ISP (Internet Service Provider) you can arrange to have BT TV via that service - but note that you need at least an Infinity package to get sufficient download speed and you may want to consider whether a 20 Gb per month allowance is enough for your needs, if not then chose the Unlimited package.