If you use Grab for transportation in Bali DO NOT EVER CANCEL if the driver asks you to. They get a cancellation fee and therefor accept rides they are not willing to make and then call you and ask you to cancel. But you as a customer might get blocked from Grab if you cancel too often. Even if you have good reason. So let them cancel if they are not willing to take the job after accepting your order. I dont know about Uber and Gojek but they might do the same.