I keep getting these calls on my landline. Had 2 this morning in the space of 10 minutes. Had about 8 this week so far. Everytime I pick up the line goes dead.

My phone line rental is with Sky. Can anything be done?

I dont want to change my number

Yes - if Sky offers a facility like BT's Anonymous Calls Reject Calling Feature (BT charges £1.75/month IIRC).

It can be a double-edged sword though because many multi-line switchboards show up the same so you could miss calls from firms you want to speak to and/or hospitals etc.

Its already on. But it only blocks withheld numbers and not unavailable.

I don't understand that. What's the difference? Surely if CLI is not available, it must have been withheld?