For the last few days, my landline phone has so much crackling on it, I cant make out what a caller

[AB58]

For the last few days, my landline phone  has really loud crackling on the line in and out

[Mark39]

Do you have Internet calls? Or does your phone plug into the wall socket?

[AB58]

It is a landline phone plugged into the wall

[Mark39]

First try the simple connection test here (even if your broadband is working normally): https://www.sky.com/help/articles/broadband-diagnostic-start

If it detects a fault, you may be able to book an engineer there and then.