Been onto them today regarding the same situation, you have to pay the above price if you use them but their are other companies that can do it.

The route i am going is for the min as i'm with 3 i'm taking out their 25gb mobile broadband and as i'm a contact phone user i get it for only £17.50 per month and upping my monthly contract by an extra 200 mins for £3 a month more.

The BT bill was going to be near on £40 before any of the calls have been made.

As for sky, i think that sky could sort the line out as they do phones too so i was going to ask them to hook it up.