Yes, of course it is possible to cancel any time. A different scenario is that you would like to pause the coaching process for some time. Despite the fact that both options do not happen very often in practice, feel free to share your thoughts and we'll find a solution.
Coaching is about growth and solving problems together. To do so an element of joy is helpful. Any coaching obligation would run counter to this idea and is therefore not part of my offering. I would also never ask private clients for payment in advance to make sure you are at no point in time at risk of losing money.