If you run your own business, it is important that you are doing the scheduling.
I have a major customer, and once in a while, they presume to tell one of their tenants that I'll be there at such and such a time. Whenever that is done, I correct them and tell them that I can be there at some other time. Tactfully, of course. But I am not going to be run ragged, or pressured on my schedule for someone else.
If I allowed that, I'd soon find my own business to be intolerable.
Which is not to say that I am not as accommodating as I can be, but please.