How do I stop my telephone line from crackling?

We moved into a new build house and paid BT about £100 for a 'new line'. Ever since we have had noise on the line so bad that we can barely hear people on the other end when they call us or we call people. It is so bad that we don't use it any more and rely on cell/mobile phones . BT are charging us... show more We moved into a new build house and paid BT about £100 for a 'new line'. Ever since we have had noise on the line so bad that we can barely hear people on the other end when they call us or we call people. It is so bad that we don't use it any more and rely on cell/mobile phones . BT are charging us money every month for something that doesn't work and they say the line is ok when they test it. What can I do to fix it? Do I need a telecoms engineer out?
Update: Just to add to this, I have tried another phone - same problem. I have tried the test socket behind the panel in the BT socket - same problem. Then we reported it and BT sent out an engineer who said that he couldn't find a problem. He didn't actually do anything other than pick up the phone and listen. He... show more Just to add to this, I have tried another phone - same problem. I have tried the test socket behind the panel in the BT socket - same problem. Then we reported it and BT sent out an engineer who said that he couldn't find a problem. He didn't actually do anything other than pick up the phone and listen. He didn't even open the BT socket and try the test socket. We then got charged another £100 for that before we eventually had a 20 minute rant at BT and got that refunded! However, we still don't have a line that works and don't see the point in getting BT out again as they don't do anything and then charge £100......
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