As Robbie says, ask for cancellations. It was always happening with ours. Signal would go every now and then and shíte. Told them we were not going to be paying €100 for an engineer to come out. Cancelled the direct debit at the bank and they started sending letters demanding payment. I wrote them a letter back stating we cancelled it as we were not getting the service and there is no activity from our box and anymore letters from them demanding a debt that doesn't exist would incur in an admin fee of €200 per letter.
They didn't send anymore letters but rang and offered to send an engineer for free so we accepted. About 6 months later it went again. Sent an engineer for free again. 6 months it went again so were like WTF is goin' on so we rang an independent installer and he came and pulled the dish and cables down and the state it was in was laughable! They Sky "engineers" were using shitty knock off cabling and connectors and then fuckin' sellotaping them together and sellotaping them to the dish!
The indy charged us 100 quid, gave us a free HD+ box, new dish, rewired the whole thing and tacked it neatly down the side of the house, sealed the hole in the wall were the wire came from the roof to the box and on top of that got us all the channels except sports for €52 a month!
Happy days! Rang Sky to complain and post their shitty parts back to them and they gave us 2 months free on top of what the Indy gave us and told us they'd send the "engineer" to collect the parts.
That was over a year ago now and we've had absolutely no issues with our signal or service.