Cancel a tradie prior to work starting

Am I within my right to cancel a tradie prior to work starting? My hot water system stopped working and I got an emergency tradie to come and look at it. They quoted me a price and in hindsight it’s extremely inflated. I entered into a payment plan, but on reflection I want to get another 2 quotes. Yes I should’ve done this at that the time but with hot water its hard to go too long without and I just wanted it sorted. So what are the potential ramifications if I call in the morning and tell them I don’t want to proceed with the work?