[MovedGoalPosts]

I would suggest your better approach would be to work out financially what you did loose by not having the phone line and instead incurring costs on your mobile. One you have that, plus the cost of your landline phone rental that gives a basis for assessing your real loss.

To ask for an indefinite period of cheaper service won't happen. You may get a discounted service for a few months but that would be about it. You may be better off asking for a credit to your account in excess of the financial losses you can account for.

With domestic services there is no service level agreement, and thus no entitlement to "compensation", anything you get would be a goodwill gesture.