you can ask, but there is nothing in it for him. If the next person dosent want a telephone account for example if they already have a mobile, then when you leave it'll be disconnected, and whoever wants it reconnected in the future will just have to pay again. In my experience, if you want a phone line you pay for it to be installed yourself, and ask the landlords permission. Some will say no as they dont want to be stuck with another bill if the tennant does a moonlight flit