Billing complaint

Yhoo where do i start, i a Wifi co tract with them, but i dont know how they do their billing, i pay every month end but every 15th i get cut off and its really irritating and whenever i ask i get a flimsy excuse that i am owing. My understanding is that its a pay as you use. I am in a vedge of cancelling the whole deal and move. Even now its cut off and i am dealing with suppliers via email and i cant work now as my type of work i have to be connected. Will never ever recommend it. They have bad service