If your phone lines and broadband are with BT and you have a fault with the line, you will need to call BT direct.
BT will need to speak to you direct as they will ask you some questions around your equipment before they agree to send out an engineer.
When calling them, just quote your phone number so that BT can identify you.
The number to call for reporting a fault on the line is 0800 121 7667 option 3.
Please also be aware that BT may charge for a wasted engineer visit.