correct course of action to take

what to do when person in a higher position is attempting to control my earned leave. i need advice on what say or do to correct this behavior.

due to staff members not communicating when they have to use leave, the supervisor would struggle to find people to cover the others for breaks and what not. we had a meeting about it with the supervisor and i agreed to changing schedules with those who needed it and when it was needed. But after the supervisor left the person higher in position to me told me that i can't use my leave one hour before my shift is over. which doesn't sound right because that was not what was discussed. note that my appointments are only about once or twice a month, is this the expectation?