My line has never worked properly

I had the line installed for my dad and the cables were ****** the line didn't work for over 2 months where I was billed, they then came and set it up again where it only worked for a few days and was suspended due to non payment. I made a payment and the line hasn't worked since. I've called in numerous amounts of time where I spent no less than 45 minutes and it has still not been resolved. The line has now been suspended again due to non payment. So I've made arrangements to pay and when I got to the technical department I was given even worse service. I am expected to pay 1400 for a line that hasn't worked and I've already paid 750 for a line that weve probably only used for a few days!