Laying your own telephone cable (from demarcation point)
Step 1: Bring your router to the demarc point and verify that it works there. You did not mention if you had done this, but if not, you should, as the whole point of a demarc is to say: "If it does not work here the provider needs to fix it. If it does work here the problem is in your wiring." So you need to test that.

THEN you can start to concern yourself with the wiring onward from that point. Which appears to bear no resemblance to the North American standards I'm familiar with...