Moved to new provider but still being charged by Sky

[CrustyJugglers]

I moved away from Sky to BT at the end of last year, and received their emails saying services cancelled, sorry you are leaving etc. I was given a smaller bill in December which I assumed was the final portion of the contract, but had just checked my account and noticed that for some reason my direct debit is still active and I'm still being charged (£20 more a month than the december price) for sky TV six months on, despite both my boxes being unplugged and stored in the garage! 

How do I go about contacting Sky to stop them taking money and getting a refund for the last six months? 

[Mark39]

BT can't cancel your Sky TV contract. You have to do that, by contacting Sky to give the 31 days notice required.

[PandJ2020]

...which means there will not be a refund as you are still contracted for the services even if not using them...

Because you haven't cancelled this is why they haven't asked for the boxes back yet.

The cancellation and reduced bill are due to the broadband takeover only.