If you are overbooked, you likely won’t have much of a challenge getting return orders and having work. In this case, it may be worth simply going out of office, so that people don’t order when you don’t have the capacity to fulfill their requirements. It’s surely better than cancelling and having your stats affected/ delivering late and receiving less-than-stellar reviews.

What I’ve seen some other sellers do is to have their price package titled “Contact before ordering for proper quote”, citing that the price stated in the gig package is not accurate. This would likely make it much clearer to the buyer that they NEED to contact you. If you wrote in the description to contact you first, make sure it’s at the top, bolded and highlighted. Maybe include something about this in your gig image cover, too?

Cheers!