Repeating Calendar Entries don't allow individual edits

We created a recurring calendar entry to staff our Design Gallery for team members. When a customer wants an appointment in the Design Gallery, we planned to edit or delete that day's Design Gallery appointment to be open then add the customer appointment in that newly opened slot.
We can't delete or change a single calendar entry from a recurring set of entries to allow us to insert a sales appointment instead of a Design Gallery appointment. MBC deletes or changes all of the entries rather than the one on the given day. We've tried cancelling and completing the entry for that day but MBC won't allow us to add a new appointment in that slot. As a result, we can't use the recurring calendar entry for these appointments - we have a schedule so team members work in the Design Gallery same times/days each week and thought the repeating Calendar Entries would work for us. Unfortunately, it is not.