Was explicitly told that rented flat had working telephone lines and could be connected to the internet. Where do I stand legally if this turns out to be false?

I moved into a flat less than two months ago and recently set up internet with Plusnet. I received my router yesterday and plugged it in, however I'm unable to receive any internet, even after speaking to Plusnet on the phone. I'm probably going to have an engineer be sent over, but I was wondering where I'm likely to stand if it turns out that none of my telephone lines actually work? I never would have rented this property if I hadn't been explicitly told that the phone lines were working (which really anyone would fairly assume just by seeing telephone jacks). Is it possible this would breach my contract, since the lease was signed under the pretense of having working telephone lines?