ANY ideas on this phone fault ?

[JOE.MADDISON]

for 5/6 weeks using land line to land line call to my sister i get one ring then silence,her phone does not ring,if i use a moble i get through,she can ring me no problem and i can ring other numbers, shes bt im sky,bt have tested her line and say its ok,sky say they see no line fault,but say they will pass this strange problem to openreach ?????????

[JOE.MADDISON]

Sky engineers traced fault to my sisters phone/answer machine somehow my number was blocked,now cleared and working