T's will tell you their policy about paying or not; they're like doctors, you pay to go to them and if you don't go, they can't suddenly fill your place but if they're not there, you don't have to pay so how can you "bill" them? It doesn't work in that direction when you hire someone; you don't ever get paid by them, just service for money or no service for no money. They're running a business, you aren't, you're the consumer; if your T is absent too often, unexpectedly, find another one who isn't.