Minor changes (like the start time) should be discussed and agreed on in the chat for the event booking. If you discuss the change over the phone, make sure to note it in the chat as well and have the Music Lover respond in writing, so there’s always a clear record of any changes.
To make a major change (such as changing the date of the event), the Music Lover will have to cancel the current booking and request a new booking with the updated information. You will not have a cancellation fee if the Music Lover cancels the event.