Hi F12 and sorry to hear about your landline being constantly engaged. I've had a look at your line details using the information we have on here and can see a problem. The line details for yourself and a different customer of ours are the same which may explain the issue. I've removed your number from the switch as I can see an engineer has already been arranged to take a look and I've fully noted your details with the data for our Telephony Provisioning Team.
When the engineer arrives, he'll check the cabinet outside and speak to our Telephony Provisioning Team so they can check the current line location and other ones for you to get it working as expected. I'm sorry about this but do pop back on here after the visit if you're still having problems.
Thanks,
Lisa