how do I let customers know that I'm fully booked?

Is your calendar updated? Usually when your calendar is updated they won't contact you. However, there has been times I will get a request even though I've blocked out my calendar and I respond by saying I did not have any availability left that is why my calendar is blocked off (not in those exact words, but you know what I mean) and they'll say "yeah I know, I just thought I'd ask anyway."

If you are looking for wording you can say something along the lines of, because of the high demands of the holidays, I am completely booked. Thank you for considering me. If you need additional help you can contact Rover support at _.

My first suggestion is to make sure to keep your Rover calendar updated. That being said, I keep my calendar updated and I still get requests even though I've marked myself unavailable. I use the standard Rover message for I'm not available, but I add a phrase at the beginning to say something like, As shown on my calendar, I am not available.... The standard Rover message is tactful and positive and says something to the effect of please keep me in mind for future bookings.

It depends on if I'm unavailable for the entire stay or only part of it. I'll either politely decline ("Unfortunately, I'm unavailable during this time period. Thank you for the inquiry. Dogsocks sounds like a great dog, and if you need a sitter in the future, please keep me in mind!"), or offer alternatives ("I am fully booked on [dates], but I would be happy to discuss options for the remainder of the dates you require. I offer pick up and drop off services for $, and I'd be happy to pick up Fluffernutter on [day] if needed...").

If I can, I'll try to refer to another sitter I trust, or I'll include the Rover support line.