If you have an ordinary Sky box it is part of the contract that you have it connected to a telephone line for 12 months. After that you can disconnect it. Or you can pay Sky an additional fee and they will waive the telephone line. If you have one box my advice is to connect it to the telephone line tell Sky that you have done so and then disconnect it some time later as they do not police this.
If you have Sky Multi-room however both (or more) boxes MUST be connected to the telephone line at all times because Sky DO police this and they WILL send you a bill for a full subscription.
t
March 2007